Maintain current weight!

Hi I am a 5'4, 143 lb male. I started using MFP last year. My starting weight was around 187 lbs and after using MFP and exercising, I lost 50 pounds in a span of 3 months(Dec-Feb). After reaching 137 lbs, I stopped using MFP and went back to my normal diet. As of now, I gained around 7 pounds since I stopping my diet. I feel bad because after the hardwork that I have done, I am now gaining weight again. What can I do to maintain my weight to 135-140 lbs? Please help! Thanks!