15.4 weeks I think it's twins!

Mirriah
So this is my 3rd pregnancy, we have a 5 yr old girl and 3 yr old boy. Both pregnancies were different and I knew the gender right away, mother's intuition or something. With this one, it's soo different I'm certain it's twins! I had a super positive test at barely 3 wks-I had barely stopped peeing on it. My boobs are so sore, I had extreme sickness from about 2-12 wks (never threw up with either singleton), my emotions are WAY more crazy, I'm gaining weight faster now, my nose is much more sensitive... I know every pregnancy is different but this one is too different. I had an u/s at 7 wks and they only saw 1 baby, but when we went to hear the heartbeat last week it took my Dr awhile cuz she thought she kept hearing the echo of mine... I'm only 23, and we conceived naturally, but still! What do you think??