Using the Pill for contraception

So I’ve been on the pill for about 5 months now, not for contraception but to regulate my period. So, i haven’t been taking it regularly and i normally take it haphazardly throughout the day whenever i remember.

I recently lost my virginity to my boyfriend (safely of course).

And we’ve been discussing not using a condom and just my birth control. I was wondering how long i should be taking it regularly before it would be safe? And what test i should take to check for stis?