Needing a bra but....

Hey ladies... after one year of the same bra i am sad to say it really is truly time to buy a new one. I wear a sports bra because I’m too active to let my boobs bounce everywhere. I gained weight which is why I’m needing a new one. The one i have now is getting too small to where i can barely put it on everyday since i wash it everyday so it “shrinks” i guess you could say. I no longer know what size i am and i can’t afford to buy a decent one so it will have to be from Walmart. Does anyone on here know how i can find out what size i am? Or does Walmart allow you to try them on?