I just want to touch on a few aspects that I'm seeing that relate to the "health issue that you have a question on"...
You have a grand trine between Pluto/moon in the 12, Mars in the 4th, and Chiron in the 12th. These houses are ruled by water and these planets are also in water signs - makes it a tad more powerful and I would expect some strength from this positioning. It is a relatively close grand trine and I would expect that this would give you some stamina and the ability to be quite tenacious especially with the Pluto and Mars involved. You also have a Scorpio ascendant and they can be angular with very little body fat. So, while you say that you are frail, it doesn't seem that necessarily needs to be so from what your chart is saying to me. Do you work out at all, do weights or yoga, anything with body strengthening?
You do have a 1/2 of a grand square with the uranus in 2nd, venus in 5th, and jupiter in 8th and this was completed about 2 years ago with Saturn's transit through Libra and maybe at that time, trouble with relationships, friends, money and maybe a lack of a support system. More recently, points of the cross have been activated by transits of Pluto and Uranus and especially, Uranus possibly causing some electrical energy hence, the nervousness maybe being more pronounced and as a result, weight loss. These transits are still in the area but are going to be dispersing over the next year or two - check your ephemeris for the dates.
There is also the pluto/moon opp to sun/mercury and since the sun/mercury are in the 6th and are expressed through that house, it could indicate health issues as to what you were asking about -- nervousness and in this case, a mental nervousness. Maybe a mind that has trouble calming down. (Chamoile tea helps with sleeping by calming the mind.)
Lastly, there are a series of sextiles in your chart - quite interesting and such that when you have planets going through virgo on transit, they would complete the last two sextiles and go completely around your chart. This would indicate a time when I would expect that you should be feeling better as long as there are no other adverse transits (although, it would create one oppostion but, on the other hand, it would also create two trines and two sextiles).
I am seeing "nervous energy" in the chart and depending on transits, could be worse or better ... doing something to calm the mind and body would help. What doesn't help is doing nothing - that energy has no where to go and as a result, stomach upsets. Dancing is an activity that could also work.
Note, this was intended to address your question of being frail and having a nervous stomach and did not attempt to look at other areas in your chart.