Recurring Nightmares. Mental illnesses.

I've been having nightmares very frequently. In the dreams, I am in my room, sleeping and it looks realistic initially, except few changes. I mean I'm not sure at that time if I'm dreaming or I'm awake. Then suddenly someone comes in my room and I realise that I'm dreaming and this is not real. At this point of time, once I realise that this is a dream, I try to wake up by making some kind of sound, but I'm not able to speak,in my dreams. Then I try fiddling with my phone, (still in my dream) hoping that the noise by phone or alarm would wake me up. Eventually I am successful and I wake up screaming. This has been happening very often and each time it's scary because at the beginning of the dream, I am not sure if I'm dreaming or awake because it's so realistic. Details look perfect, for. e.g. in the dreams I'm wearing the same clothes I  actually wore before sleeping. I don't smoke, drink or do drugs. I have no family history of mental illnesses.