My iPhone won't respond to touch

My iPhone won't respond to touch! I've restarted my phone by holding the home button and the power button many times, but it still won't work. I know it's not a glitch because I completely erased and restarted my phone, with all new data, and it's still happening (Thank god I backed it up first on my laptop, I redownloaded all my info a few days ago), so it must be something with the device. My phone is also doing things for me, like texting people random letters and taking photos. I have no control over it except the home and power button. I don't know how to fix this, should I just get a new phone or is there a way apple can help? I'm thinking I might have to replace the battery or screen... I also know it's not the new update because this has been happening since before I updated it. Also, the 'glitch' is on and off. Sometimes it works, sometimes it doesn't. The longest its been frozen is about 24 hours straight. How can I fix this?!