You need to find a INFERTILITY doctor (REPRODUCTIVE ENDOCRINOLOGIST)in your area. ASK your OBGYN who THEY suggest. Don't give up--sometimes they will be able to tell you WHY...and sometimes it will be diagn. as un-explained infertility. It took me 6 years to get pregnant. I had IVF, and had triplets.
I echo triplets comments. 5 years, a number of surgeries, IVF and twins for me. Go find a good fertility doctor. Good luck.
I'm so sorry to hear that it is taking you so long. If you have been trying for four years consistently, then you probably do need to see a reproductive specialist. This may sosund dumb, but are you sure you're timing is correct? A lot of women think they should TTC on the day that they ovulate, when in reality you should be trying to about 5 days before. You may already be aware of this, but many couples think they have fertility issues when they really have timing issues. Also, are you keeping track of what's going on with your body? Are you periods regular? Are you certain that you ovulate? Do know that your luteal phase is long enough? If you're pretty confident that every thing is normal with you, then it may be your boyfriend. The only way to know for certain is to see a DR and both get check out. I've reccomended this before, but it is not a personal reccomendation. Some women believe that accupuncture helps with fertility problems and conception. Again, I can't speak about it personally, but you may want to consider that as an option. Good luck to you!