You are still early in the game and only 4 weeks out. Yes, it could be the mayo but it could also be a message from your tummy telling you to hold up and go a bit easier with softer, more digestible foods for another week or two. Have you tried fish and meats before with success? I've been through it all in the last 6 years with RNY surgery in 2006 and revision due to bleeding ulcers in 2/2012. No way could I get tuna down after 4 months no matter what was mixed with it after 4 weeks--includes both original and revision surgery. Sprouted Tofu is a good substitute and I've learned to appreciate it. Good luck!!!!