12 week pregnancy means 1st trimester or 2nd trimester ?

Dear mums , This is my first pregnancy. 12 week pregnant. When is my second trimester is starting? 12 weeks means am I already in my second trimester? Because my First trimester was horrible and I had a very terrible experience with morning sickness from the first few weeks, even I couldn't eat properly. I feel hungry, but when I eat I vomit all of them. always I feel empty. I have heard most of the time we can eat after the first trimester #12 week pregnancy