Summer ? Under 18's please tell me the truth ...?

Okay so i am a size 10 in English Clothing (usa-6) And its coming up too summer and i was thinking now that ive lost all the weight (i lost 3 stone) maybe to start wearing a bikini at the beach - AM I FAT ??? - The problem is that i have stretch marks on my waist, thighs and behind my knee. They have almost faded but you can still see them because they are white. I dont even like wearing a 1 piece swim suit or even show my bare legs because i am scared people will laugh at my legs. So do you find stretch marks distgusting cos i do ! Should i wear a bikini ? Am i Fat ? thx