Hello Jacinta and welcome to the forum.
Congratulations, a second baby, how lovely for you and your partner.
I agree with Garfield, walking is an excellent exercise for just about anyone I would think so thatâ€™s a start. Just remember whatever you do take it slowly and build up over time. Also if you feel your eating habits arenâ€™t great then look at what you can do to clean them up. Cutting down high fat foods to start with. Nutritionally though you could perhaps get a plan from your doc so you can make sure the baby isnâ€™t missing out on anything it needs.
I donâ€™t have children so not sure about all of this but there are a number of ladies on here who do have children and may be of more help.
I wish you every success on your weight loss journey.