For one, as we women age, it's harder and harder to maintain and lose weight, due to the slowing of our metabolism. I just hit 40, and I notice a difference for sure.
The other symptoms may just be related to you being out of shape, but you really should have a thorough physical done and tell your doc what's been going on. One you get a clean bill of health, you can ask your doc for some diet guidance, and possibly even a referral to a nutritionist.
Good luck!
Do you eat a lot of carbohydrates like bread as these add to weight gain.