People don't believe I am pregnant.. :(

I'm only 13 weeks and one day. I had a miscarriage last year. And I'm 17 a senior in high school. And I had a teacher that said to me I don't believe you are pregnant you also sai last year you was and I said yes I had a miscarriage last year and she said that I told her before we went on summer break I am pregnant and i said yes I did but I had just found out then and now I am 13 weeks and she said I still don't believe you and I said I have a belly now as before I did not. I use to cheer I was rather little but now I have a somewhat baby bump not huge lol but small to medium size. What do you all think?