Your proper weight should be around 115 pounds. In my opinion, no matter how strenuous your daily work is, you should do moderate systematic exercises, combined with deep breathing, from ten to fifteen minutes, morning and night. I note that you say you have had rheumatism, and as you are underweight you might be suffering from poison in your system resulting from a torpid liver or from constipation. Many girls suffering as you are find that this is the case. Keep the bowels open and the blood circulating at all times.