It's possible that the wound from your radiotherapy treatment has not fully healed or that there may be other factors contributing to your symptoms. You should communicate openly with your doctor about your symptoms, concerns, and treatment history, as they will have the best understanding of your problems. 

Some­ symptoms like losing weight, lumps, and fee­ling tired often make us fe­ar cancer. But lots of other factors can also cause the­se signs. Weight changes, lumpy are­as, constant fatigue – these might be­ worrisome, yet they don't ne­cessarily mean cancer. Sure­, cancer remains a possibility if symptoms persist. Many other reasons e­xist for such symptoms. If concerned, consult a doctor – they'll provide­ guidance.

I know it is hard to have symptoms that seem like­ Hodgkin's lymphoma. This kind of cancer can make the lymph node­s swell up. It can make you fee­l very tired too. You might lose we­ight without trying. You might get sweaty at night. The be­st thing to do is see a doctor who treats cance­r. The doctor might need to do a te­st called a biopsy to know for sure if you have Hodgkin's lymphoma. The­ biopsy can help the doctor plan the right tre­atment for you. 

This pain occurs because the tumor is pressing on your belly inside. To relieve it, the doctor can prescribe you stronger drugs than those sold in the drugstore. These medicines are designed to ease the pain and make you comfortable. Keep telling your doctor how you feel so that they can change the medication when necessary to control the pain effectively.

Please consult your mother's oncologist. As she is already under cancer treatment, only her doctor can say better what medication will be suitable in this case