I don't know how you can avoid sexual sin, when you're putting yourself in private space, with two exposed people, and moving the bodies toward the act of sex.
But at this date, I blame The Church, for accepting the Sangerite Lies that our Young Adults need to naturally have more control than we'd expect from a Widow.
Jesus tells us he will give a way out of temptation. Seek him.
Don't go out alone with your date, and don't take your date where nobody else can see you. If you think this "boring" and "too restrictive" then make immediate plans for your wedding, where after you Own each other, you can be as alone as you like, and do almost all those things your flesh wants, without sinning. Be straight forward with the other adults in your church, you both desire to have sex, and God said sex is for marriage, so Let's Go! Be prepared to get a ton of advice to not get married so young, but if you really can't control yourselves, be honest about that too, and do what you can to get married. Be ready to work hard to understand your spouse, as all couples must do, be ready to forgive, as you'd both likely still be young and learning even of yourselves.
If you actually wouldn't marry this person, then you shouldn't be playing with your reproductive organs with this person. Period. Why would you want to give that first experience to someone unworthy of you?