how can you tell if you're having twins.

Sarah

I will be 7 weeks Monday I haven't went to my first appt yet but I have severe nausea I'm having lower pains in my belly. I went to my primary care Dr a week ago they did a blood test I was 6 weeks they said. but I was having these pains starting at about 4 weeks. my stomach already get super hard and then it un tenses. I feel like I'm a tad bit bigger than I should be. I've already had to buy new clothes I couldn't wear mine much past 4 or 5 weeks. I'm hungry every 1 to 2 hrs and I'm so tired and I feel like I'm going to vomit on and off all day. and on top of that my breast have already almost doubled in size. I had small petite breast to begin with but theyre so sore and I feel like there is already so much milk trying to get ready for the baby I have huge knots under my nipples almost as big as my entire breast now so my boobs are very hard. twins run in my moms side and dads side of the family. I hope to find out soon. any advice or opinions