I Was Having Sex With My Girl Friend( Not For

I was having sex with my girl friend( not for the first time), and i lost my erection before i ejaculate. Since then, my penis is very weak, im unable to sustain an erection for more than 1 minute. I also noticed im not having morning erection and when i have it, it would be very weak and soft. Its now 2months with this stressful situation of mine. Pliz help