Destinysdaughter I second those who say you need to be comfortable with yourself first, and you need to develop your own self-esteem.
How you do that is going to depend a bit on your caring responsibilities - does your Dad live with you, do you have respite care opportunities, etc?
What sort of person do you think is good, cool, worthy of admiration and respect? Who do you secretly want to be, and why? That's not "what do you want to have", but "what things do you admire in other people?"
This doesn't have to be solely about relationships - work out where you say to yourself "oh, how awesome" about anything that someone does - mountain climbing, football, zoo keeping, politics...
Once you've worked out who you'd like to be, then think about what it is that you respect in those people. This is often stuff like determination, working hard & consistently, resilience, kindness, empathy, imagination and resourcefulness, self-efficacy.... i.e. all the things you're already showing by caring for your Dad.
Caring duties can be overwhelming at times, so perhaps rather than thinking about dating in any spare time, can you use that time to do something that challenges you a bit and requires you to use all the skills you respect? It could be anything - I took up long-distance running and climbing mountains at the time I realised I was bored and unhappy in my career (which had stalled) and that my relationship had broken (because all my exP respected about me was the outward appearance of my successful career). Exercise is good because it's good for you and requires relatively little thought once you get over the initial barriers, but it has to be something you really want to do, and preferably something you didn't think you'd ever do.
Work on that for a year or two, keep thinking about who you want to be and what you'd accept in terms of appropriate boundaries and kindness, keep reading Mumsnet (AIBU and Relationships)... and a few years down the line you may discover you actually have a very good radar for acceptable relationships, and healthy self-esteem. 