Don't be too hard on yourself, pregnancy is a great but at the same time exhausting experience (or so I hear, no personal experience yet, unfortunately ). Maybe set yourself a goal where you want to go - a bit of shopping, or going for a (non-alcoholic) drink somewhere, or maybe a trip to the library? I find it's easier for me to go out if I actually have a goal, not just going for a walk.

You could send a bit of hot weather up here, it's freezing!