Two kinds...
The first, a public tongue with interpretation, aka prophecy. No interpreter, keep quiet.
The second, an in-private tongue between you and God.
I've color coded the differences here:
https://christianchat.com/blogs/prophecy-and-tongues-differentiated-part-1.174929/
https://christianchat.com/blogs/prophecy-and-tongues-differentiated-part-2.174930/
(And let me know if you need an interpreter to read it. My computer and this website are at odds about font sizing).
I assume the private tongue is the one you spoke about, saying it was a different language every time and that you had no understanding. Most, not all but most I've known have a regular 'language', it could be you are new and haven't 'learned' yours yet? But together with not having understanding, it raises a yellow flag for me.
Paul said he didn't understand at first, then asked for understanding and received it. I followed the same pattern and got the same results. What I found is to pray like Paul ultimately did ... pray what you can for something in english (or whatever your native language is), which you understand; Then if you are praying sincerely your heart and mind will continue on with that 'subject' while your lips then speak to things you don't know about ... but God does. I pray for danja in english, then I pray for danja in a tongue. And together I understand that the Holy Spirit and I have prayed for danja over both the known, and the mysteries, that surround you
Test the spirits. It is only by the Holy Spirit that one can say "Jesus is Lord". At times when I feel like something might be interfering with my prayers, I start repeating "Jesus is Lord" "Jesus is Lord" "Jesus is Lord"... If you're ever unsure about where a language is coming from, start saying that. It'll help ensure that your lips are the Lord's, and not affected by some outside influence.
God Bless you
Tongues are the inspired prophecy of God as of Pentecost spoken in all the languages in the word, words with understanding coming from the lips of God .and not just Hebrew as before the time of reformation .(The veil is rent) Words by which men can believe God... the source of Christian faith and say amen. And not..... what was he trying to convey? As in do I have the seek the understanding of one seen as a private interpretation?
I would suggest first things (the things of God) first.
We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:
Knowing this first, that no prophecy of the scripture is of any private interpretation. For the prophecy came not in old time
by the will of man: but holy men of God spake as they were
moved by the Holy Ghost.2 Peter1:19-21
Also we should remember the warning in 1 John 2:26-27 as to the spirit of the antichrist who were there .as those who n make scripture without effect by forbidding the work of the promised anoiunting Holy Spirit not seen as our teacher as a he teaches us we abide in him not seen .Not men seen like the Pope .
These things have I written unto you concerning
them that seduce you.But the anointing which ye have received of
him abideth in you, and
ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as
it hath taught you, ye shall abide
in him1 John 2:26-27
Tongues, as the prophecy of the Holy Spirit, (God's living abiding word) speaking through men, woman Jew and Gentile alike signaled by Pentecost is the fulfillment of Prophecy found in Isiah 28.
Stammering lips are the mocking lips of God who mocks those who refused to hear prophect as a sign
against them .They are shown as not entering God's Sabbath (rest). God, not seen, mocking those who mocked him be rather following after the oral tradition of men as that seen making prophecy (the word of God) without effect
For with stammering
(mocking) lips and another tongue
(other than Hebrew)will
he speak to
this people.To whom
he said, This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet
they would not hear.But the word of the Lord was unto
them precept upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little; that they might go, and
fall backward, and be broken, and snared, and taken.Wherefore
hear the word of the Lord, ye
scornful men, that rule this people which is in Jerusalem. Because
ye have said,
We have made a covenant with death, and with hell are
we at agreement; when the overflowing scourge shall pass through, it shall not come unto
us: for
we have made lies our refuge, and under falsehood have we hid ourselves: Isaiah 28:11-15
The fulfilment of prophecy
in the law
(Isaiah 28:11-15) it hath been written, that, `With other tongues and with other lips
I will speak to this people, and
not even so will they hear Me, saith the Lord;' so that the
tongues are for a sign,
not to the
believing, but to the
unbelieving; and
the prophesy is
not for the
unbelieving, but
for the believing,1 Corinthians14: 21-22