Medication Weight Gain and Injury

Hi there everyone. I am trying to lose weight after increasing my dosage on a moderately weight-gaining medication and being injured from pulling a hip flexor. I am now 5'11" and 170 and would like to get back down to my previous weight of 135 if it's possible on this medication. I am trying to get back to taking walks now that the weather is getting nicer. Hopefully this injury heals one of these days. I'm feeling a little bit defeated. I'm so used to being slim.