I'm glad you've found a nice parish to attend! Thank God!
Seems like you've got two very challenging things in front of you right now. One is being a young single mom, the other being a catechumen. The really great part is that your child is going to grow up in the faith. You will also be 'growing up' in the faith (we all are), and though you're probably a great mother already, you will likely be a better mother as you grow as an Orthodox Christian.
It's also really good that you are aware of what you are feeling, and not just running out to find something to do to distract yourself from loneliness. Those are just feelings, and they come and go. Different people need different levels of social interaction.
I don't know you and your general life conditions, and I'm not in your parish, so it's difficult for me to see what you are experiencing. Sometimes people are at different places in life compared to their peers, and I've heard it expressed that it can be quite frustrating and lonely at times. Sometimes it's a person in their twenties watching all their parish friends get married and have children, then suddenly, everything is different, and they haven't found the spouse for them. What they do is stick with it, and they get involved in other appropriate activities for them. They live Orthodoxy, but the parish is not their social mainstay. Having a child is a full time 'activity' though, and sometimes mothers just need to talk with other adults. A parent, especially a single parent, really does get a lot of opportunities to "deny yourself and take up your cross". And yes, that is a gross understatement. Ideally, parents have each other, and when you don't have the 'other' half, you have to be more self reliant and learn to trust God all the more.
Sounds like you are keeping contact with your previous friends, and that is good. There isn't any reason you can't be friends with people who don't share your beliefs. Doesn't sound like they've given you any reason to not be friends.
Sorry, that's not a pat solution. Just take it slow, be steady and patient. Feelings come and go, and part of the Orthodox way is that it isn't just about our feelings. You will have some outright temptation as you draw closer to Christ and His Church. That is typical, not that temptation isn't there after one is Orthodox, it's just that we learn better skills to deal with it, spiritual warfare, and we have the Sacraments to help us as well. At first we're not very well armed, so we learn from others and pray, and with God's grace we grow. As a catechumen, the entire church is praying for you every Divine Liturgy, and I will be remembering you too.
There is actually a lot in Orthodoxy that will ultimately help you navigate better in the world. I've been pretty amazed by it. Sometimes I was inwardly eye-rolling and thinking how stupid some of our social parish gathering activities are, but later found that exact skill to be very useful in a challenging work situation.
The goal is Christ, and if we make some good and true friends along the way, it's a bonus.
May God bless you and your beautiful child.