Trimester?

B🐻🎀 • Married to a handsome Marine ❤️💙 & Mommy to a sweet little boy! ☺️
So I'm 13 weeks 1 day today and I can definitely feel the top of my uterus just below my belly button. It kind of freaks me out.. Lol can you ladies feel it also? And glow tells me I'm in the 2nd trimester now but I thought that started at 14weeks? Can someone tell me when the 2nd trimester actuall starts because I'm now confused!