Hey, I was just wondering if I could get some help.

I'm a 17 year old boy and have been having loss of appetite and nausea lately. For the first couple of days, my poop was a little bit runny but still solid for the most part. However as the days go by, my poo gets runnier and runnier. The only comfortable position is laying down, however I always get the feeling that I need to use the toilet. But when I go to use the toilet, very little or nothing happens. Also whenever I eat, I don't eat as much as I used to and feel the need to use the toilet straight away.

Can someone please help me, I'm sick of feeling like this