My advice is ask your HV about groups in your area and be brave and go try them out.
You'll be pleasantly surprised I'm sure.
Some are better than others but hopefully you'll find a good one that suits you.
Do you have a Sure Start centre in your area? If you do I would highly recommend making use of it. I went to my local sure start centre and found it fantastic.
There were Mums of all ages, from young Mums 16 + to women late 30's. We all got on well because we all shared something in common being new Mums.
It'll do you the world of good to get to baby groups, your baby will enjoy them and you're likely to meet new friends out of it.
Good luck, definitely make the effort to go along to groups in your area.