Can't handle public tantrums anymore!!!

My 21 month old is starting to have tantrums all the time! If she doesn't get her own way or doesn't want to leave she will go mental and just flop around on the floor! Today was the last straw! We were at a play centre and I had to literally drag her out by her arm! She was hysterical! I was mortified! I had to carry her all the way to the car with her kicking and screaming and I'm 30 weeks pregnant! Then I couldn't get her in the car seat as she was thrusting her body around! This was the second tantrum whilst we were there! She had one when we first arrived! I try to stay calm and tell her no but it doesn't work! I completely lost my shit and cried all afternoon! I'm due my second in 10 weeks and have no idea how I will cope! I refuse to take her anywhere now! She's awful if I have doctors appointments as she throws tantrums then to! How the hell am I meant to cope in public situations with a newborn and a toddler throwing a fit! Seriously! What the fuck!! My friends tell me way I deal with it but nothing works!!