Hi there!
Many congratulations on your new arrival!
I am a Pilates Instructor who specialises in pre and post natal Pilates. I am also Mummy to a beautiful boy too!
Firstly, whatever exercise you plan to do, it's best to wait until you're 'signed off' by your midwife team - you usually have a check around 8 weeks (or somewhere between 6-12 weeks) with a doctor/nurse who will assess you and hopefully tell you everything is fine and you can begin exercising. Make sure they test the diastasis recti - this is how well your abdominal muscles have 'knitted' back together. Exercising with a large diastasis can cause damage to the muscles and give a 'pot belly' look!
Are you breast feeding? This is something to consider too as this can zap you of energy. Certain types of exercises can inhibit milk production so it's best to have a chat about it with someone in the field.
I'd be happy to give you a free consultation, if Pilates is something you would like to consider. I found it really helped bring my core muscles back post birth and tone up! I can also do the diastasis recti test for you. I teach 1:1 in the client's house - to fit around the client and their little one, or in group contexts. Message me if you'd like more details.
In the meantime, I found during the first few weeks, plenty of walking with the buggy and maintaining pelvic floor exercises was enough to begin shifting the weight.
good luck
xx