I have had a really big poo stuck in me for 2 days what shall I do?

I am so embared to say but 2 days ago I tried to go to the toilet to do a poo however as much as I pushed the poo wouldn't come out, it was soo painfull & I felt like I was pushing out a baby. I am only 15 and this has never happened to me before. I find it hard to sit down and when I'm walking around the house I feel like something is trying to come out of my backside but whenever I sit down on the toilet seat its a diffrent story, another thing is in the last coupleof hours I felt like I was gonna puke. Please please please I am actually crying whileim writing this, please help me!