Tips for small guy?

Im the smallest guy in my gym, im currently 5”8 and 130lbs and a new purple belt. Id consider myself a hobbiest as i don’t compete but i go roughly 3 days a week. The vast majority of my partners are 200lbs or over and I’ve been having a hell of a time actually using my jiujitsu against them. It seems like anything i try just immediately gets shut down, regardless of what it is. It’s taking a big toll on me psychologically because they all make a point to tell me that they are “not using their weight” when i do have a good round. Will gaining weight help at all? Should I switch gyms to one with people closer to me in size? Im currently doing no training besides just jiu jitsu and hiking, would adding resistance training help? Thanks.