DR request just walking but I want to do more.

So I’m 13 weeks and started this pregnancy over weight I’m not trying to go all crazy with workouts but I want to incorporate some sort of light weight training with like 5 lb dumbbells for my arms and upper body. My dr just suggested walking. I wanted to use my elliptical or indoor cycling. Now I’m confused. I’m self conscious already and I just want to try and be fit this pregnancy hence the word try. Lol kinda wanna just do some 5 lb arm workouts and just go from there. Need advice. And I know gaining weight is inevitable I’m just trying to gain the what’s recommended nothing extra.