AIBU about this.

[Shootfirstaskquestionslater]

Me and my DP have talked about getting engaged I kind of proposed to him but we have decided to put the idea on hold because we haven't been together very long and I got in to a bit of a panic I'm not in work because of depression and anxiety and I changed my mind about getting engaged because I can't work and he does he would be supporting the both of us which doesn't seem very fair to me and I worry that he will end up resenting me if he's tied to someone who can't work. I admit that my self confidence is very low and I do always think that he can do so much better than me. We have decided to get each other promise rings instead. AIBU for thinking the way I do. He thinks am being daft.

Have a child!

Exactly @flouncydoves

Why on earth are you involving your family in life decisions when you are 3 months into a relationship.

This is bonkers.

The person is a strange at 3 months. Just calm down and get to know the person properly.

Another vote for 3 months being far too short a time to get engaged. Take your time, ignore the pressure from your family and tell your sister to pack it in. Are they this involved in every aspect of your life? Sounds like they could well be contributing to your anxiety and stress.

The OP also is thinking of having a child with this person

After 3 months, even "partner" is a bit of a stretch, unless we're missing background like this man has been your best friend since you were 4-years-old and you've secretly been in love with each other your entire lives long.

Have you been in many relationships before? Most people would find 3 months far too soon to commit to a lifetime together (some are still dating multiple people at that stage and aren't even exclusive) so combined with your anxiety, it seems like a strange amount of pressure to put on yourself. You really don't need this.

I would also question your family's motives behind this - are they trying to get you married off to the first man they know is showing an interest in your, or do they genuinely think you're good together and have a future? It just seems weird of them to be so vested in this.

3 months in? Enjoy still getting to know each other, open to whatever possibilities come next.

OP, i think you should try to find someone in RL who is wise to confide in. You seem to be wanting to rush things, and I don't think this would be in your best interest.
Do you have a counsellor, an older friend, a school or college tutor?