I would have to agree. Also, how long have you known your girlfriend? I’d say your family might be concerned because 13 months is a relatively short time to know someone before deciding you want to move in with them. If you had been friends for, say, a few years before dating then that’s a bit different. But it is your life, nobody can know the outcome of any choice they make beforehand.
Getting your own place near her if you do move is likely to serve you better in the long run, though. It would put less strain on your relationship and if things didn’t work out, you wouldn’t be left homeless, needing to move back in with your dad or stuck with someone you didn’t want to be around.