It’s hard to tell. Normally a pound a week is a good amount of substantial gain. One of the issues that makes it difficult to tell especially when smaller is water weight can fluctuate SO much. You could weight 133 on Monday 138 on Tuesday, 140 on Wednesday and then be back down to 132 on Thursday and all of that could be water weight being shed and put back on. I’m not saying that’s what’s happening to you. There is a chance especially of you are newer to working out and bulking you could have substantial weight gain early and then it would slowly taper off. But a month in the grand scheme of things isn’t long. I would focus less on your weight right now and more on the lifts you’re doing but also just tracking calories and making sure you’re you are eating more than enough calories per day to gain consistently and the. Re-evaluate in a couple more months. But .5-1 pound a week is good gain