Only gained 1 lb

I am a bit worried when I went to the doctor last month they were like oh you didn’t gain any weight weird and now I will be 17 weeks on Monday, my next doctors appointment and I weighed myself this morning and I’ve only gains 1 pound . I have a proper little bump and sometimes I swear I can feel baby moving or rolling but I’m not sure yet, use my ag home Doppler once a week for two minutes and hear a strong fast heartbeat… anyone else not gain any weight and still have a healthy weighted babes? I’m worried that he’s too small … you wouldn’t think so from my bump