I'm on the pill and when I have sex with my boyfriend, he comes inside me. Afterwards, I always let it run out and clean the outside of my vagina. The rest comes out in my underpants later and I wash inside with my finger when I shower. Should I wash it out straight away instead of leaving it for risk of infection, or does it clear itself sufficiently like having a period?
There is a risk of sexually transmitted infection simply because he's ejaculating inside you. You can't reduce that risk once it has occurred.
And trying to douche or wash out the inside of the vagina only inclines you to things like yeast infections and vaginal imbalances more: that's a harm, not a help. So, it's always better not to mess with the inside of your vagina: it's a self-cleaning organ, and it's healthiest when we let it do its job alone. You not only don't need to try and wash inside your vagina with your fingers, that's a habit you should stop.
So, if you want to reduce the risks of infections, your boyfriend needs to be using condoms. That's the only way we have to reduce those risks. If and when you've both been using condoms for six months, and being monogamous for six months, AND each have at least once, but preferably two full and negative STI screens each, then it's okay to start talking about going without condoms, because the risks at that point -- unless your monogamy status changes -- would be greatly reduced.