not gaining weigh from 3weeks till 17 weeks now

It depends on individual. I also didn't gain any until I'm at my last trim. This is my 4th. For my 3rd pregnancy, because I lost to much so even though I gain back, is also gaining back my pre pregnancy weight. So long as the baby is healthy upon Dr checking and you are eating well (not say gpin on diet) then it will be alright.