I need to loose weight during pregnancy

During my last pregnancy I gained 25 kg (50 lbs). It's been 1,5 years and so far I only lost 8 kg (16 lbs) from right after the delivery. In spite of my hurting feet and knees I didn't manage to loose more weight. I started working early and due to an seemingly endless commute there is no time to sign up at a gym or group.

I might be pregnant again now and I'm horrified that I will gain even more weight. It's already too much the way it is.

Has anyone successfully and healthily lost weight during pregnancy?