Depo Shot causing weight gain?

I started the depo in October, in the first 3 months I didn’t gain any weight, or lose any for that matter. I went in around March to get my 3rd shot, and had gained a good 15ish pounds since January and March. Also since being on the depo I don’t get my period anymore at all, which is nice. My doctor thinks that the depo is not the reason for my weight gain. I eat the same, and I’m fairly active. Do you think it’s the depo? I don’t want to stop or switch off the depo because I like and would prefer to not get my periods anymore. Thoughts?