Plumbing help!! Toilet water not coming up except when i flush and nearly overflows?

I just got a brand new toilet a few days ago and it was working fine until earlier. When I tried to flush it water came down but it didnt flush and i tried again and more water came down and nearly overflowed. Then it just went down very slowly until no water remained, leaving all the paper and everything at the bottom of the toilet. This is the only bathroom in my apt. and its a big problem.. I hope to try and get my plumber who isntalled it tomm. morning but i need help as soon as possible thx!!