Blah relationship

I've been with my BF for almost 3 yrs and lately things are just so blah. There's no spark there's no fun there's no spontaneity anymore. We get along great. We hardly ever fight. The kids are happy and have more than they could ever dream of. I have two boys and baby on the way. We have sex but it's not very often and it's not exciting anymore. We just go through the motions and that's it. We hardly ever kiss.....how the heck do we get out of this slump?! Or is this just part of having a family??
**update**
We were invited on a camping trip the wknd of the 5th of August. We weren't going to go because we will be gone the wknd before and my BF doesn't like to be away from work that much and because I'll be 20 wks pregnant with our third and sleeping on the ground doesn't sound like fun right  now to me. But I might just suggest that we go! We NEVER get to do anything with just us anymore and this would be the perfect opportunity. Even if it is with a bunch of couples our age who will all be drinking (I can't 😢).