Lower half of Iphone not working

Hi. For a while my iphone has been doing this thing where it has a kind of ghost touch. I could leave my phone unattended and it start acting if someone was using it, but it would would glitch and switch form app to app not letting me even be able to use it. It's been ongoing for months but it was stop from a period of time then start again. Today however, it just stopped working. It was working fine this morning and then the home/unlock swipe then just stopped working. I am un able to actually use my phone as I can't swipe up to unlock it. I can't switch from apps or even send messages to anyone. There is no way I can afford a new phone at all, so I was wondering if there was a way for this to be fixed. I've had this phone for just over 2 years, it's a little cracked but not major.

Thank you. Taniesha.