Please help! What is the best mouthwash to use if you have receding gums or sensitive teeth from that problem?

Gum recession. Gum recession does not respond to mouthwash use. There's a reason why your gums are receding and mouthwash will not stop the recession. A Fluoride containing mouthwash, such as act or phosflur, may reduce sensitivity. N to address the recession issue see your dentist, or ask for referral to a gum/bone specialist, a periodontist.
Gum recession. That's not the answer! there are many reasons for gum recession, some of which are poor oral hygiene, improper brushing, occlusal trauma, parafunctional habits, etc. You need to have your dentist, preferably a periodontist evaluate your mouth and discuss the specific factors in your case. Then he\she can offer advice regarding prevention and treatment.
See dentist. If your gums are receding at age 37, you need more than a mouthwash. See your dentist. He may refer you to an periodontist.
Fluoride rinse. I would stay away from any mouthwashes that have alcohol in them and use a rinse that has Fluoride as the first active ingredient, because it will help reduce sensitivity of the teeth.