Ren, yep, it is very normal. Before I started mat leave I would be struggling to keep my eyes open come 2pm and zonked out on the couch as soon as I got home. Once I started mat leave, I enjoyed my sleep-ins and nanna naps for about a week before DS decided to show up early! So, rest up as much as you can, put your feet up whenever you can and enjoy it because once bubs is here, it's non stop broken sleep for a while!