How to get bigger breast?

So recently I ended my breastfeeding journey. While breastfeeding, my breast were a nice size and filled my shirts out nicely. After drying up, I'm left with basically no breast at all and its having such a huge toll on how I see myself in the mirror. I almost look like a little boy. Its making me super insecure. I tried going bra shopping to find some cute ones to make me feel better. I couldn't find anything that fit. Is there anyway I can get bigger breast without surgery? My metabolism prevents me from putting any kind of weight on. The only time I've successfully put weight on was after getting pregnant. Would getting on birth control help me gain a cup or two? Or is there anything I can take?