No, it doesn’t sound dumb at all. In fact, statistically, 90% of relationships break up over two things: sex or money. If a couple is not compatible in these two areas the relationship is more likely than not to run into serious difficultly.
The good news for you is that (1) you are very young, and (2), you recognize that there is a problem and you are making an effort to address it. The bad news is that if your boyfriend is unwilling (or unable) to meet your needs then you’ve got a hard decision to make.
There are a number of things that can contribute to a man’s decrease in sex drive — stress being at the top of the list (change of job, financial difficulties, etc.). On the other hand, you mention that his lack of desire became apparent almost immediately, which causes me some concern…. I can’t help but wonder if the two of you are just not that sexually compatible. Needless to say, it’s a lot more satisfying to be with someone whose needs, drives and desires are more closely aligned with yours, than not. Equally, when there is a drastic difference in partners needs and desires infidelity is likely to ensure and the relationship (generally) will not last.
My recommendation is for you to have a serious, non accusatory, non threatening, discussion with your boyfriend about how you feel and the fact that your needs are not being met. Ask him if he is willing to work on improving the situation with you. If he does agree to make an effort to work on the situation — and then follows through, you’ve got a good shot at making the relationship work. If he doesn’t, I think you need to consider finding someone who is more compatible with you.