What's wrong? (Girls only)?

I just started my period for the first time in February, then had it again in March. But I haven't had it for 4 months. My mum said it happens when you first start. But I used to masturbate when I was little, I didn't know what it was, but something tempted me and I did it again, I feel so stupid. I always had this fear of becoming pregnant, please don't tell me I will be? P.s. I'm only twelve