Ejaculation when not fully erect.

I had protected sex for 3 times in span of 5hrs on 28th Mar and since then I am not getting proper erection. I tried for 4th time but I couldn't penetrate since I wasn't fully erect. Also, while having sex the 3rd time, my penis misjudged the angle and got a jerk / dashed on wrong place inside vagina. Hence, we didn't have sex for the 4th time and I ejaculated while oral sex when I wasn't even fully erect. Since that day until today (more than 3 days now) I try to masturbate.. But ejaculate before I am fully erect. Also, my erection doesn't sustain if I stop stroking. It was all normal before the third sex on 28th March. I don't knw if this is normal or all in my head to perform on bed with my fiance. Can this be because of nervousness? This was my first encounter with sex and may be I m conscious to perform with my fiance. Also I am not getting early morning natural erection that males get when they r out of bed.