Can I exercise if I have osteoporosis?

Yes, and it is preferable if you do. However, there are certain guidelines to follow so make sure you have a trainer who is educated in osteoporosis.

I am gaining weight, what can I do?

When all is said and done- eating less and exercising more is STILL the best formula for ;losing weight. Looking at WHAT you are eating also counts. For the more mature woman, eating less wheat seems to have a good effect on weight.