masturbation and morning/spontaneous erections

I have had this problem a couple of times during the last six months. The usual series of events would be like this:

1. everything seems fine, i.e. about an average of 4 masturbations per week
2. things turn bad if I masturbate on consecutive days without leaving "recovery" days in between
3. first, i would lose morning erections. I would even have difficulty masturbating - as I would get only weak or even no erections at all
4. taking a gap (from porn and masturbations) of 2 weeks or so - and my morning erections would return.. first morning erections would be weak, and further rest would see strong morning erections
5. if i restart regular masturbations, i would go back to step 1 (i.e. all the problems return and the cycle begins again)

please help. what could be the problem? Your assistance is highly appreciated.

PS:
1. i am 26, unmarried, never had sex for cultural/tradtional reasons
2. i haven't experienced spontaneous day time erections for quite some years - though i can have erections when masturbating or morning erections, but not both (masturbation cancels morning erections)
3. i was recently diagnosed with severely deficiency in vitamin D and low vitamin B, and have taken multivitamins and vitamin injection during the last couple of months

25Hydroxy-Vitamin D3 --> 5 ng/ml (range 30 to 150)
vitamin B12 --> 230 pg/ml (range 191 to 663)

4. i am not sure if porn is causing these - although i do not think so - and i have cut back porn use in any case