How to really know if your pregnant when your on birth control ?

I know it sounds crazy , but ive been having some weird things go on with my body /stomach lately .... so I hVent gotten my period for 15 days its been a month since I switched my birth control to the one I have now the last time I’ve had sex was December 4th ever since then I’ve been getting these weird flutter feelings in my stomach for a quick second but they keep coming back , frequently using the restroom if I don’t go pee it’s like I’ll have a drop of pee in my underwear with white discharge at the same time . Idk never been through this can somebody give me advice !