Starting again

I'm a 73 yr old young at heart female. I have arthritis in both knees (painful) being obese doesn't help the problem; it also affects my lower back. Well last year I started 1700 cal eating plan and did light exercise; recorder everything on MFP lost 30 LBs in 3 mos, knees felt better. But I gained it all back due to stress eating sugar carbs. Well I'm starting over with the same health issues with less stress and more determation. I'm 200 LBs. Need to lose at least 40 LBs. I need all the encouragement, tips and prayers I can get