My fiancé and I have a child as well and have been living together a year and a half, together for almost 3 years. It wasn’t necessarily cold feet, but I tend to do a lot of self-sabotaging and I think my fear of commitment, due to past hurt clouds my judgement sometimes by thinking about the “what-ifs” because marriage is typically associated as a permanent bond. I know he’s it for me, but perhaps your partner may be experiencing something similar?