You do sound like you have lost your confidence, which is very very easy to do after a baby and you have additional reasons which make it harder. That said, all your abilities are still there, you sound like a very promising student, and it's just a question of tapping into that again. I don't think you should aim for the MPhil alone, but the whole PhD and I think you can do it, I did mine alongside having children in a part-time stop start format and did eventually get there.
Firstly- check you don't have any type of PND, because doing any type of academic work when down/depressed and untreated would be very hard. If it is just feeling down/out of the loop academically, that's a different thing.
I also think you are missing a trick by not using Facebook and Twitter, with tight security settings. If you are are disabled and stuck in the house a lot for that reason (I don't know if this is true for you) or just with limited time, then FB is a good way of keeping in the loop- and there is a group which could be really relevant for you called:
PhD and ECR Parents Group
which has over 1,000 members I think! Its a closed group so you ask to join and then you have lots of people in a similar situation to you.
I'd also join Twitter professionally if you think you might like to go on academically, you can just set up an account for that purpose, follow people that are relevant to your work and to your discipline and dip in and out of it as you choose, this is especially relevant if you are wanting to make a career out of academia and want to follow happenings in a particular field. This might not be so relevant in your discipline- in mine, a lot of key people are on Twitter and a lot of policy stuff comes out daily which is of relevance.
Good luck with it all, once you do your data collection, you will get more of a momentum, you could also try online podcasts for PhD students (e.g. Tara Brabazon) or some of the writing ones like Shut Up and Write Tuesday UK on Twitter. There was a thread the other day about motivation to write, and there was some really excellent advice on that thread.