Apps opening and screen lighting up

i bought my iPhone back in january 2015 and have had no problems till this past week or so. It opens apps by itself and the backlight decides at random to light up when in a phone call while it is on speaker and sitting on my lap. I never am touching it when all this happens and my screen is perfectly clean (I'm very good about keeping a clean screen as I hate it so dirty). It happens when the phone is plugged in and when it is not plugged in. Always while I'm on speaker phone with it sitting on my lap or table. I have tried everything from resetting it and a factory reset but still nothing is working. I need help as I wonder if I have a virus or something. I have not jail broken the phone or anything like that. I have everything updated including latest update and updated all apps. Please help