UHF pool party and a bikini...?

So I am going to a pool party next week I just found out today my friend wants me to wear a bikini with her. I told her yes. But I don't even own a bikini! And my stomach is a little flabby. I have been working out for a month. Lost about 6 or 7 pounds. But I still think I'll look fat in a bikini. I am 5'8 150 pounds. My legs are what I dont like. They are fat and I have stench marks. How do I even ask my mom to buy me one?