It's a long time to wait and you get the initial excitement and then life just carries on. You still have to work, carry on with social life and other commitments. Your bump will get bigger in the next 4 weeks or so and that will help. The when you leave work for maternity it will really hit you!
Honestly though you are lucky to not have all the nasty symptoms I hope it stays like that for you.
And congratulations I am 20 weeks too with my third!