If it was me feeling this understimulated I would be heading back to work but I know you say you are pregnant so perhaps not an option for you!
Babies/toddlers can be boring to be around. I'm currently on maternity leave for soon to be DC2 and I find days with DC1 (18 months) quite long and tiring sometimes (hence why DC1 is in preschool three days a week). The rest of the time I divide into little chunks which helps the day go quicker.
We do lots of activities but they are free or very low cost, eg we have breakfast, then will take a ball to an outside area or playground (and have morning tea out, so a snack at the playground or as a treat, a coffee and cake at a Starbucks, Costa etc). We'll come home for lunch and a nap, then do a food shop in the afternoon as DC1 really enjoys that, or go to the local public pool for a swim in the baby area, or do something crafty like play-doh. Or I crank up some music and we have a dance party in the living room - something silly like that.
Every other week we'll do a soft play and/or a lunch out.
I'm sure there will be some free playgroups near you so you can have a bit of adult chat with other mums and dads (there's nothing like that near me unfortunately).
Then it's the teatime, bath, bed routine. I find that's the only real time we're sitting in and playing with DC1's toys. If I'm having a tired day there will be a lot more than that! And Peppa Pig will buy me 10-15 mins so I can put my feet up and have a little cuddle time.
Reading that back it sounds like a lot but I have a very active DC who needs running out, and I always enjoy the days when they're busier because like you I find being at home quite boring!