Hi there, I really appreciate this service!

My long time monogamous partner and I opened up our relationship, and we are trying to understand our risk tolerance for sexual encounters with others. I am 36yo transmasculine (no bottom surgery), and my partner is 42yo cis female. 

I recently started seeing a gay cis man who engages in higher risk activity than me (unprotected anal with other men). He's very transparent, and tests regularly. He takes daily PrEP and doxyPEP after high risk or unknown exposures. We have ongoing talks about safer sex, but I would benefit from education here. I'd love if you could provide a comprehensive risk analysis for giving/ receiving different sex acts. I want to feel knowledgeable in making the best decisions for me and my other partner(s). 

So, could you please give me an overview of how likely I am to contract HIV or an STI from giving/ receiving oral/ anal/rimming/vaginal sex. What about oral with no ejaculate? Fingering? Frotting? I use condoms for all penile penetration. 

Thank you!

"Comprehensive" might imply you're expecting more than this forum can provide. A several thousand word essay would be required for a truly comprehensive assessment. The risks are highly different for different STIs, and of course also depend a lot on the nature of your sex partner(s) going forward. At one extreme, the risk is nil for a partner who is tested regularly and recently tests negative (for those STIs for which accurate testing is generally available); but even this sort of partner is very likely to have HPV, for example -- since almost all sexually active persons have been infected and at any time half or more have active, transmissible infections. There also are unresolved controversies, such as the frequency with which gonorrhea is transmitted by kissing among men who have sex with men (MSM). All in all, among anatomical males, the receptive partner in anal sex is generally at highest risk for HIV and most STIs; the insertive partner in anal sex next in line; next would be the receptive partner in fellatio; and finally the insertive partner in fellatio. There are no data on the extent to which ejaculation affects risk, but it is logical to assume the receptive partner is at increased risk for those infections transmitted primarily by fluids (HIV, gonorrhea, chlamydia), and that it makes no difference for the insertive partner. There also are issues related to how and where one seeks sexual partners:  completely anonymous events (like "glory holes" in bath houses or sex shops) and other quick pick-ups (bars, bath houses) are generally considered especially high risk. Commercial (paid) partnerships are generally considered higher risk, but often without good data for this assumption; and some commercial partners (like escorts, meaning expensive sex workers by appointment) probably are at low risk of having a transmissible infection.

Among different STIs, HIV is just about the lowest risk:  unprotected sex between discordant partners (i.e. one with and the other without HIV) still results in virus transmission typically under one chance in a thousand, compared with maybe a 50% (1 in 2) for gonorrhea. Preventive treatment, i.e. PEP and PrEP for HIV, doxy-PEP against chlamydia and syphilis, are important too. For HIV, whether or not the infected partner is on effective treatment is a very important determinant.

In general, fingering and other hand-genital contact are little or no risk for any infection, even when genital fluids are used for lubrication. Kissing has long been considered to be generally risk free, but as noted above, maybe not for gonorrhea.

I'm glad to see you plan on condoms for all penile insertive events, or of your partner(s) if you are the recipient. But be aware that condoms are only modestly effective against infections transmitted primarily by surface contact (HPV, HSV, syphilis), while nearly 100% protective against those transmitted in fluids.

For HIV, estimates published by CDC in 2017 for contact with confirmed infected partners and assuming the infected person is not on treatment: