Relationship not exciting anymore

Hey guys, so I’ve been together with my boyfriend for 3,5 years. We’ve had a great relationship and we love each other. I basically would like him one day to be the father of my children... unfortunately I don’t feel really happy... it’s not like I’m sad all the time. I really enjoy his company but I feel like something is missing at the moment.. I hope it’s just temporary... We also haven’t had sex for nearly three weeks...

have you guys experienced something similar? Any tips on how to spice things up a bit?

I really need help!!! Don’t know what to do!

Thank you all!!