How often do you/should you let your man cum inside?

Hey guys, I recently went on the pill and have let my boyfriend cum inside a few times once I knew I was protected. I was worried before but now that we have done it I feel more at ease and I've let him do it many times but today I woke up with a horrible burning sensation in my vagina and yesterday it was quite irritable too. I feel that I might have a UTI and I'm worried that it's linked to my man cumming in me. I just wanted to know, is there a certain amount that people tend to do it? Do they let their men do it every single time or do you limit it to a certain amount? I'm very scared when it comes to infections and things because I seem to be quite prone to them and I'm aware that the pill doesn't prevent STI's or any other infection so I want to be responsible but I haven't got a clue how much is average or anything, thank you!