If you want to wear one then do it. It breaks my heart to look back on my younger self, lying on a hot beach in a one-piece, because I had no idea then how to wear a bikini.
I have now bought myself two wonderful Freya bikinis - proper bra sized, bra styled bikini tops with proper bum-covering bottoms - and they have changed my life. I'll never wear a one-piece again.
Don't buy the silly ones from cheap shops (unless you are v slim and small boobed, in which case grr, I'm jealous), spend a bit and go to the lingerie section of a decent department store.
Buy bigger bottoms than you think you need (they'll look terrifyingly huge on the hanger, but flattering on your hips) and try on a range of top sizes to get the right fit and support.
I can honestly say my Freya bikini top gives me a better bust than my best bras do! Money well spent.