I can totally relate to that. I have been there before. When I was in graduate school I went through a 2-3 year dry spell. No sex whatsoever. It ******* sucked. It is not natural for men to not have sex and for men sex is more like a need than a want. That said, a dry spell is serious business and my short term advice to you would be as follows:
To break the dry spell consider the following:
1) Consider taking meds for depression/anxiety. My 2-3 year old dry spell ended shortly after I was diagnosed with generalized anxiety and other psychological disorders. I was put on Prozac and Lorazepam and my social anxiety andover eagerness around women went away and I was able to bed some attractive women just because of my changed neurochemistry. You might want to also take a few drinks to loosen you up. Keep in mind if you have a substance abuse problem this medicinal approach might not be a good idea but it did get me out of a slump.
2) If you have the financial means, consider becoming a "sugar daddy" whereby you give a girl an allowance in exchange for a dating-like relationship which usually involves sex. Most of the time this is technically not prostitution and you are not breaking the law . The other advise might be to go a jurisdiction where prostitution is in fact legal and partake. Just be sure to use protection. The disadvantage of these approaches is that they are costly and you might not have the means.But if you do, it will certainly bust your slump.
3) If your problem is that you are just being too picky, loosen your standards and have sex with any woman, even if she is fat and unattractive. Again the idea is to break your slump.
The above suggestions are just bandaids. Once you bust your slump you can focus on a long term self-improvement plan. But it is hard to think long term when you are thirsty in the desert. A long term self improvement plan would involve things like working out, improving social skills, increasing your confidence, becoming more financially secure, dressing better,and learning more about how to approach women. There are lots of books out there on dating, some better than others.
Alot of guys think that their height or their ethnicity holds them back with women. This might be the case for your or it might not be. But if it is, just remember that the world is a huge place and there are 3.5 plus billion women out there and chances are you fill find a woman to have sex with you regardless of your height or ethnicity. You just need to be persistent.