My boyfriend slept with a prostitute and then i had protected sex with him after. but he gave me unprotected oral sex. is it likely for me to get hiv?

Possibly: If your BF indeed gets infected with HIV from the prostitute (assuming the prostitute has the disease), then you are at risk for HIV as well as other STDs. If you are concerned, avoid all unprotected sex until he is found to be HIV negative and STD free (may take 3 months to be sure). Get yourself tested as well. However it is unlikely to get HIV from oral sex.

No: The risk of transmitting HIV for a female receiving oral sex is very low, but not zero. Several factors are reassuring: your boyfriend probably DOESN'T have HIV, the concentration of virus in saliva is typically very low, etc. He should be tested for HIV, of course, within a week or so of exposure and again at 6 months. PRACTICE SAFE SEX or consider a safer partner? Best wishes!

No but Possible: Oral Sex is not safe sex but it MAY be somewhat safer. We don't know for sure because there is an under-reporting bias in the "oral arm" of studies that compare unprotected oral vs unprotected vaginal sex. People assume oral is safer so they tend to attribute any STDs to the unprotected vaginal sex rather than the oral sex. So it is possible depending on HIV status and timing.

Let's talk: If the two of you really care about each other -- and a couple in a long-term romantic relationship should -- you should promise each other that you'll have only safe-protected sex if you go enjoy yourselves elsewhere. You should also, from time to time, go and get checked for HIV together unless you're monogamous. Wouldn't that be the loving thing to do?