Weight gain..

Hey guys, so I started out weighing about 154 pre-pregnancy and I am 6 weeks weighing 159.. I feel like maybe I'm gaining too quickly. Is this normal? I'm not eating any junk at all, no ice cream or sweets at all and mostly organic meals. I go for long walks a few times a week..do I just need to walk more? My naturopathic doctor said I'm high risk for miscarriage so he doesn't want me eating junk or doing anything more physically exerting than walking. Any tips?