Me and my boyfriend have had unprotected sex for about 8 months and stupid I know but I haven't gotten pregnant suprisingly but not that I want to or anything, I'm just wondering could he be sterile possibly because there is no way we're this lucky. Is there anything to know if is or not?
It is always possible that the male is sterile, but you could be as well. But, it may be that you just have not had sexual intercourse at the exact right time to get pregnant. Remember, that the woman is only able to conceive a few days a month. So, unless you are having unprotected sex really frequently on just the right days, you won't get pregnant. (Yes, it is possible to get pregnant from just one episode of unprotected sex and women do. But, it still has to be at the right time in the woman's cycle.)
But, as you stated, it is not the best thing to do, if your do not want to get pregnant. Contraceptives are so easy to get and use, why chance an unwanted pregnancy?
The only way to tell if a gentleman is sterile is to have a semen analysis. This is usually the first step in an infertility workup, as it is fairly easy and inexpensive.
Again, it is always possible that the male partner is sterile (or functionally sterile). (Being functionally sterile means that the gentleman has sperm, but not a high enough count to be able to impregnate a lady.) There is also a possibility that you are not fertile. But, it is more likely that you have just not gotten together at exactly the right time. As such, protect yourself from unwanted pregnancy.
If the gentleman is really curious as to whether or not he is sterile, the only way to know is to have his semen analyzed.
We do have sex frequently and it's unprotected, there was at one point I was two months late but I wasn't pregnant I had three negatives and when I finally came one my period I bled for almost a month it was a on and off again flow but it didn't actually stop.
So, it may be that you are the one that is not actually able to conceive at the present time. If you have irregular cycles or your hormones are out of balance, you may not be able to conceive. But, this is not a good birth control method, as just at the wrong time your body comes into cycle correctly and you have sex just at the right time to conceive. The result, an unwanted pregnancy.
If your cycles are off, you should probably see your gynecologist for an evaluation. It may be that you need to be placed on cyclic hormones for a while (usually they just use birth control pills. That way you are also protected from pregnancy.)