I am 18 years old. Yesterday my girlfriend and I spent some close moments which involved some touches around the body parts. I felt something unusual in my penis after some minutes from beginning. Later I found 2-3 drops of semen in my underwear though there was no reason to ejaculate. Is this a symptom of premature ejaculation disorder? What should I do now? ( I masturbated 3-4 days ago and have a habit of doing so once or twice in a week. Is this a reason for such happening?)