How likely is it you can catch an std from just oral?

So I recently went to a three sim with a woman and a guy who are both in the gangbang lifestyle pretty heavy. I let this woman eat my ass and give me head without a condom. For intercourse I used a condom but now I’m worried because I didn’t use the condom for head too I could get something from her. How likely is it I could get a STD or STI from head and getting my ass ate.