Your story interested me from the point of view that you already have your suspicions that "over" masturbating was the cause of your problems. I suppose it is difficult to define what over masturbation is, even if it exists at all, since no doubt the amount of "abuse" a body can take varies from person to person. Indeed what each person would define as an unhealthy amount of time spent on onanism depends on a whole lot of cultural, psychological and familial factors. But failing your doctor coming up with an answer and supposing that you understand the causes of your situation, I am reminded of the following links that I posted which might deal with overcoming your problem as you have defined it. The following is a link to my thread which discussed the subject in greater detail: https://www.peaktestosterone.com/forum/index.php?topic=69.0
However the bulk of the theory comes from the following sites: http://cure-erectile-dysfunction.org/mechanism-of-sexual-exhaustion
The type of things they are discussing here don't really fit into the mainstream analysis of ED and low libido so you might want to take them with a pinch of salt. The real issue here is whether a period of abstinence is appropriate and whether you need to replenish you body of nutrients that you may have lost. Again that is something you may need to discuss with your doctor. The interesting dichotomy here is that whereas a lot of advice suggests that to maintain your sexual prowess you need to have have reasonable amounts of regular sex, these links suggest that this would not be advisable for an exhausted body. However they do make a distinction between sex with a partner and masturbation, http://cure-erectile-dysfunction.org/repower-your-nervous-and-endocrine-functions
"In sex you extract sexual energy from my partner's to power your penis to maximum size(that is when you feel your penis going numb or semi-numb with a massive erection - then you know the sexual energy stored in the prostate and penis is maximum). When orgasm occurs, contraction of the prostate muscle sends a powerful orgasmic wave back to my brain that stimulate your central nervous system and endocrine organs - adrenal cortexes, the pituitary, and testicles. After a sex like you will be surprised to find out that you are not feeling that exhausted or tired. This is because the endocrine system has been re-powered by the massive ejaculation orgasm. Masturbation cannot help you achieve that kind of recharge."
Since I've not read that anywhere else, again I would caution total acceptance. But at least they do make suggestions to overcome the problem http://cure-erectile-dysfunction.org/mechanism-of-sexual-exhaustion
"A generally good way to rejuvenate your sexual function is by using right combination of amino-acids, herbs, and vitamins & minerals.
Since over-masturbation causes unstable levels of certain neurotransmitters (Acetylchloline, Serotonin, GABA and Dopamine) one may use certain supplements that are said to promote healthy levels."
Bear in mind too that these sites might have their own negative religious or moral agenda, and that almost every man has masturbated at some point.