You're asking one of the most difficult and important questions about relationships, but the fact that you're asking at all (and the positive turns of events so far) is important in and of itself.
Both People Must Be Ready & Want It
There are two crucial "absolutes" in my mind when it comes to making love:
- First, it must be completely consensual, that is, both people must want it to happen.
- Second, both people must be READY, and this is a more difficult state to define clearly.
Feelings have much to do with sex, and you said you "felt kind of strange" and asked him to stop. You have to go with your feelings in these situations; you will probably never regret or be terribly hurt by NOT sleeping with someone. The alternative is... well, let's just say enough people have gone that road that you don't need to try it.
Your partner sounds like a sensitive, understanding guy, and if that is indeed the case, he should accept that (if it is ever to happen between you two) it may not happen the first (or even second or third) time the situation presents itself. You will KNOW when you're ready (within reason; I'm assuming reasonable ages here), and that'll make your first time special and meaningful.
I realize I'm speaking in terms that are rather hard to pin down, but that comes with the territory when we deal with emotional issues, not cold hard facts. I can only add a reference to my own experience in this area: I was 21 before situation and feelings converged for the first time, so I'm certainly not a blind proponent of "getting it out of the way" while your'e in your teens (I don't know how old you are, this is just generally speaking). In addition, in a much later relationship I resisted the opportunity to sleep with a partner because _I_ felt she wasn't ready. I was right (she realized this shortly thereafter), and, regardless of whatever else happened in the relationship, we do not regret NOT having slept with each other.
To summarize: Go with your feelings. If it doesn't feel right, wait. In a healthy relationship, it is also a good idea to keep your partner involved in the process to some degree, talking about your feelings and misgivings (or positive expectations). Communicating your emotions will help ensure that you both do the right thing.