Hi,
I am a mom to two girls ages 2 and 4 and both of them went through phases like this at around 15-18 months.
My husband and I -- hard as this sounds -- used the "cry it out" method. It is HARD, but it is effective. We would go in after 30 minutes of baby crying, and in a loving but stern way we would say "goodnight, see you in the morning" pat her on the back and leave the room. Obviously, we kept checking on her if she continued to cry - and both of mine did - but we wouldn't go in the room again (and she didn't see us until morning). We figured if we kept going in the room then she was learning that each time she cries, we come.
Anyway, the first night we tried this was the hardest -- I remember the crying lasted around 1.5 hours. The second night was around 45 minutes. The third night and so on was less than 20 minutes. By the end of about 10 days, she just went to sleep when we put her down with no crying.
Our method isn't for everyone, but it worked well for us. Both our girls go to sleep now without any problems each night.
I hope you can find a way that you are comfortable with that gives you, hubby, and baby a good night's sleep! Good luck!