Newbie.. Help!

[Booboosmummy22]

I walked 2.2 miles in 45 minutes today, in my defence I was pushing an oversized 3 year old in pram

I know this bad and I was shattered by time I got home. Left my job six weeks ago along with the small level of fitness I had. I am also pretty over weight probably obese.

So, any advice on how to improve this quickly?

Just do the same again tomorrow. And the next day and so on.

Seriously, walking is an excellent form of exercise and you will feel so much better for it.
If it were me I would keep a record of how far / long it takes each day to be able to see improvement. You can measure distance on strava if you have a smartphone.