Is it normal?!

MK

I tested pregnant on cycle day 24 for 5 times and all came back positive. I did the beta HcG test on the same day and got 81.5 miu/ml.. i did the test again today (cycle day 28 when i'm supposed to be getting my period) and the result was 517 miu/ml!!

My gyn suspects it could be twins (50/50).

Could it really be twins?! Or is the level way too high?!