hmmmm.... read over this a few times to weed out the raincoat fluff and I'll skip commenting on that. But as for the OP...
I have a few questions first, and these are pretty much standard, so please respond honestly just so that we can get a sense of what's up here:
1. What is your height/weight?
2. How many were you taking a day and at what times?
3. Am i correct to assume that this is your first time taking a product of this nature?
4. Which version of MassFX were you using - MassFX The Destroyer, MassFX Max. Strength, or MassFX (3 generations of the product)?
From what I've read of responses here already, the guys do have you covered pretty well. None of us are qualified to give you any sort of medical advice, and doing so would be highly irresponsible. Anything that we say is based on first and second-hand experience, science, and that's about it.
In my experience in working with folks who have used MassFX, and from my own extensive experience with it, unfortunately you are in the minority with your side effects. While I don't know what exactly is going on with your libido, it is not something that others have faced, atleast in my recollection. There is always a possibility that you are rather unique in the way that things have affected you. The libido boost that often comes with a test booster-type product is one that occurs while on it as well as afterwards. If you are 3 weeks out from using it, I can say with a fair degree of certainty that the product has completely left your system, so any results that you are seeing right now are NOT going to be due to MassFX. The halflife of the ingredients are 1-2 weeks and that is it. After that, free and clear. There may be another underlying issue here, and the advice to seek medical attention is warranted if the problem persists.
Generally speaking, even at your age, the libido can surge and wane. Sometimes things just don't quite work. I know that's hard to believe, and the male ego is such that we never want to believe that a hottie grinding on our junk won't do it for us, but there are certainly other factors in life that can lead to a little lack of performance. Stress is a big one, so if you are under a lot of stress from school or life in general, it can certainly have adverse affects on your drive and ability to 'perform'. Trust me, bro, it comes and goes. Being a teenager and having that giant-sized sex drive does leave you. (Then again, sometimes it comes back....which, when married and in your 30s like me, can be a huge bummer if the wifey ain't into it!!! ugh... but I digress....)
If the problem persists, then seek medical attention. For now, you could try something else to lower estrogen, but I'd honestly leave everything alone for the time being and wait it out. Like I said, MassFX should be out of you completely right now. It's a matter of time before your system will recharge and come back to stasis.
On that... MassFX is a free-test agent(s). There have never been any allegations of it being anything different - by us, by users, or by competitors. The ingredients in MassFX have always been considered to be "natural test boosters" - a broad term for something that will boost test levels. In the case of MassFX, it augments the existing testosterone to create free-test. There is absolutely nothing in there that will ever shut your natural test production down, not in the slightest. That happens when you are receiving the hormone from an exogenous source, such as a prohormone or steroid. In this case, nothing is replacing your natural production, the testes will not see fit to reduce their output, and when you finished the product, you'll see no such rebound.