Hello. I had 35 rounds of radiation and 3 treatments of cisplatin in 2015. For the constipation I've found that Dulcolax (in the pink box, pink pills) works best. I still take one tiny tablet daily.
With regard to dry mouth, non of the OTC options worked for me. My doctor prescribed pilocarpine, which I've been taking since treatment ended. I still end up with very dry moments but the pilocarpine provides the best result.
Good luck to you, stay strong.