How come I am only almost 13 weeks pregnant.. but I look about 5-6 months.. everyone keeps telling me I look so big and that you can deffinetly tell I'm pregnant... and plus I'm having twins... when having twins does that make you grow bigger faster.. my last pregnancy ended in a miscarriage at 18 weeks and I never grew and didn't gain any weight.. but now I look so big.. and I have also gained 13lbs... is this OK.. has anyone had this happen to them

Yeah you would be bigger faster. J_9 should be able to tell you about normal weight gain
I am not sure especially with twins.

Well not to be rude but commen sense your carring two babies. As am I and I am due in sep my pic is from late may and I have gained from 78-95 lbs since then. So 13 lbs isn't very much to what u will be gaining I went from 110 to almost 200. So expect to be huge! And take each pound with a grain of rice. Since weight will e flying at u. Because we happen to get to do something most women never get to experince. Is to give birth to two babies at once so be prepared to gain weight. And understand that our pregnacies do tend to be more complacted then single births.

how come i am only almost 13 weeks pregnant..but i look about 5-6 months .. everyone keeps telling me i look so big and that u can deffinetly tell im preggo.....and plus im having twins...when having twins does that make u grow bigger faster.. my last pregnancy ended in a miscarriage at 18 weeks and i never grew and didnt gain any weight .. but now i look so big .. and i have also gained 13lbs... is this ok .. has anyone had this happen to them

It is perfectly normal and expected... :) Doctors and midwives will vary a bit on their recommendation for how much weight to gain... rough average is about 40 pounds, but your doctor will let you know what they are comfortable with you gaining. You certainly want to gain enough, especially with twins, but you don't want to go over the top as too much extra weight can put undue stress on your system and leaves you with more weight after birth.
Keep in mind as well, that if you started underweight, you can afford to gain a little bit more... if you started overweight, you can afford to gain a little bit less.
Eat a healthy and varied diet, get some daily exercise, go easy on the goodies, and you will likely stay right where your doctor would like you to.