I remember at that age I was obsessed with the thought that I should be doing something to entertain him, when infact he was more than happy to sit alone and watch the world go by. I somehow felt a duty to be at his side 24/7 and makes sure he was stimulated, now I know he likes his alone time
I find when my lo gets crabby I can divert his attention by holding him by the window and counting the cars go by and describing everything that's going on and pointing out stuff 'oooh look a bus, isn't it big, look at that man he has a lot of shopping bags doesn't he, oooh look a red car...' and so on LOL
I know you say its hard to leave the house in winter, believe me I feel your pain! BUT it is so worth it once you are out. I live in an upstairs flat so its really hard, I have to go down and set the buggy up at the front door, back up to get the change bag then bring it down the bottom of the stairs ready, back up to get ds's coat etc on, leave him in his playpen or cot, get my coat on, back down the stairs with him in tow, wrestle him in the buggy. By this time Im stressed, sweating, he's grumpy and I wonder why I bother BUT 5 mins down the road we're both relaxed and breathing in some fresh air and I know why I make the effort. Being outside in his buggy is the number 1 thing to keep my ds amused!