Considering that homosexual men still top the list as far as people at risk for HIV, you're smart to be proactive with your sex life. You've actually been doing a great job. The ways to safeguard yourself is to know your partners, inquire about their status and sexual activity, to use condoms for all anal sex, and to get tested annually if you are sexually active. You've done all that.
There is some varying information among professionals about oral sex, but on this site, we maintain that it is not a risk. I have actually penned a health page about it, trying to explain in detail, scientifically why oral sex is not a risk. Certainly, if you worry about it, then the answer is to use condoms for oral sex. There are definitely other STDs you could get via oral, so it isn't a bad idea.
Basically, though, it's quite simple. If you always consistently use condoms for any penetrative anal sex, and you don't share IV drugs, HIV will NEVER be a concern. It's really that simple.
Read this for some reassurance, and then get busy getting back to living life, as you've worried for far too long already.
http://www.medhelp.org/health_pages/HIV/HIV-AND-ORAL-SEX-THE-FACTS/show/1278?cid=68
Your test proves you don't have HIV. If you continue to have anxiety despite the test result, then it may be time to think about getting some professional help to address the anxiety.