So I recently had sex and got on birth control but after I had sex a few days later I started smelling a smell it wasn't bad but wasn't good either so I shower every morning so the smell goes away but when I wipe after I pee it brown on the tissue so I don't know the cause I've searched every std symptoms and I don't have any of them so I'm not sure what's wrong so please help! Also all this didn't start till I recently had sex I've only had sex with one person and when I started my birth control on a Thursday I had sex on a Sunday and Monday then days later all of that occurred. Ive had sex with him before I got on birth control and this never happened.

First you do understand, that you need to be on most birth control pills for at least one month, for them to be effective. Having sex a few days after starting birth does not give you any protection. So there is of course chances of pregnancy.
So this sex really had no protection.

Next of course you can have a STD, some do not even have any signs. One with just an order, is common also. Also there are many infections possible that can happen, that are not STD's but still need to be seen about.

So you go to your local doctor and get an exam, also discuss birth control with them, since you need to be more educated in how birth control works.