Advice From Someone Who Has Been There?

Yesterday was my boyfriend and i's 4 year anniversary. We are in our early twenties and started dating when we were teens and I should mention that  I'm 3 years older than him. He is 20 and I'm 23. ( yes, he was 16 and I was 19 when we started dating) We love each other and we have a connection that I have yet to find with anyone else. Also, we were each other's first.
And we just moved in together a little over a year ago...
After 4 years, we feel like our relationship is at a stand still. Since he is only 20, we are not ready to get married or have children yet- the things that could liven up a relationship. We admitted to each other last night that sometimes we feel bored and at times, we want to experience that new love feeling. Is this normal? We both agreed that we want to try to make it work and get past these feelings but we are not sure where to go from here.. Any advice would be great!