I recently had a tvu, wihich showed a thickened uterine lining. the doctor suggested it may be adenomyosis. could it be uterine/ovarine cancer?

Yes but unlikely: I suppose it is possible to have uterine cancer when the lining is thick. There are simple in office and in the operating room ways to get a sample of the tissue and make sure. But more likely the doctor thought the uterine muscle tissue was thickened which is a different part of the uterus which is usually adenoymosis.

Doubtful: A thickened uterine lining could be adenmyosis(just a thickened lining). At your age it is doubtful it's anything else. The only way to be sure would be to get a biopsy of the thickened lining.