Your risk is so small as to be almost non-existent. First, he said he was clean, which most people are honest about (although not all). If he didn't have HIV, you can't have caught it. Second, you were tested at 30 days. If you are concerned, you should get tested again at 45 or 90 days, but you really shouldn't be concerned. Third, you apparently did not let him ejaculate into your mouth. Now, there still could have been pre-seminal fluid (pre-come), but the quantities of that are not usually very great, and as long as you did not have cuts in your mouth from brushing or flossing, or as long as you did not have open sores, you shouldn't have any concerns.
Even if he were HIV positive and even if your mouth did have cuts and sores, the odds of your catching HIV from giving oral sex, while real, are not very high.
You should relax, but if you stay worried, get tested again at 45 days, which will give you at least a 95% certainty. At 90 days, you can test with 100% certainty, provided you have had no real exposures in the meantime.