Erectile Dysfunction for Jelqing?

Hi guys,
About 2 weeks ago I started to practise jelqing. I started approximately 20Th December. My plan was 3 day on and 1 off in semi-erection. In the beginning I started with 50 stokes (3-5 second), and later about 100 stokes.
For 2 weeks, I gained in girth and length. Not much, but I did.
But, 9Th January (this was a day-off), on this day it was month and 2 days without masturbation. I was really aroused. So about at 1PM, I jerked off, and it was really good. Fountain of sperm came out of it. Everything was fine. At least I didn’t find out anything uncommon. About 5 hours later, I was like: “Let’s get another round.” So I jerked off again. The pleasure was even bigger. But after orgasm, my dick suddenly went flaccid almost immediately. I thought it was just tired. So I went to bed.
I woke up in middle of the night. And I felt like my dick was dead. I was so desperate. I didn’t sleep all night long because of it. Morning after (today), I woke up without morning erection, which is weird, because I’d had it almost every morning until then. I am scared that I messed up my erection, which was until this day on really high level and never had trouble with it.
Can my dick just be exhausted, or there’s something more? Can it be from stressful ordinary days, because I am an athlete and my day is just waking up early, go to school, from school I run home to eat something, then I train, I go out with my girlfriend (she doesn’t know what has happened to me, and I don’t want to tell her, I because don’t want to disappoint her) and then I come home, eat something and go to bed.
I’ll appreciate every tip and advice, ‘cause I am desperate. Thanks.

(SORRY FOR MY ENGLISH)