It's not a sin, but it does sound like it's at a point where it's an irrational fear - which isn't a sin but definitely isn't good. I wouldn't say that if it were the sex thing alone, but it sounds like being close to men, in general, are a part of that fear. I suppose it isn't such a big deal if you aren't wanting to get married anyway, but it is if you are. The fact that most men want to be intimate with their wives isn't even really where you're going to find the problem; a good husband will love you even if you are not physically capable of doing that. The problem is a lack of trust. You will not be happy long-term married to a man you won't trust, and neither will a man be happy when he knows his wife doesn't trust him. But like I said, if you aren't wanting to get married then it doesn't even really matter.