I'm sorry you're feeling so low :( it's gruelling being a mum, especially to a lively 18 month old! I struggled to speak to people & went through pnd, but I forced myself to go to toddler group & ended up jointly running in after a year or so, talk about throwing myself in at the deep end!
Things that helped me were getting outside, even for a trip to the park, woods, beach or to the shop for a paper... the exercise & fresh air make you feel better & break up the day.
Speak to your HV, they've heard it all before & can offer support and maybe some ideas to help.
My DS is at school now, I'm still shy but have made one really good friend after swapping numbers at a birthday party last year & for me, that's enough for now, I'm not hugely social.
I also do voluntary work, which has given me my confidence back :)
I've recently started learning to crochet too, which is cheap & relaxing! Needle under two pounds, wool from pound shop - there are videos on you tube.
Lastly, keep on here - there are chat threads & meet ups etc, the silly threads can be good company sometimes!