You have a lot of reading to do!
L-tryptophan can cause muscle weakness! And other problems.
http://www.supplements-and-health.com/tryptophan-side-effects.html
You mention two different supplements -- tryptophan and a metabolite of it, 5-HTP. Most people don't feel anything from taking tryptophan because it isn't very successful in crossing the blood-brain barrier. When the FDA banned it because of a tainted batch and left it banned for years, 5HTP from a plant was discovered and became the favored way to take it because it does cross the blood/brain barrier. But it seems whatever form you're using is working, you are metabolizing it, and it's making you tired, as it's supposed to do. This might wear off over time, it might not. When used as an antidepressant, 5HTP often acts like one, with side effects such as sedation in the beginning that eventually a person gets used to. 10 hours of sleep a day is a lot, and too much sleep can also leave you feeling drowsy and weak just as much as too little can. You might be a person who just doesn't need that much. But the answer to your question is easy enough -- stop taking it and if the weakness goes away, you'll know it's the tryptophan. You can even try a smaller dose and see if it works for you without the lingering effects.