I'm reading your question and your So What Happened. Since you don't have a PCP, I'd say to get one - an internist or someone in a family or women's practice. Assuming you are in generally good health, one practitioner can handle your basic needs for general health as well as birth control, Pap smears, etc. You would need an OB/GYN if you had a special gyn problem or of course if you had another child, but there is no reason to get one at the moment if you are pressed for time and finances. The OB/GYN can't/won't do everything your PCP can do. This has nothing to do with the fact that you haven't been back there in 2 years - of course they would welcome you back. But you need someone else for basic needs.
I know you have put your child first, and while that's admirable in many ways, think of the flight attendant speech - "Put the oxygen mask on yourself first and then assist your child." Helping yourself is essential for proper care of your child. And do get a babysitter when you go to your appointment so your doctor has your undivided attention. You can ask friends, you can ask your OB/GYN for a referral, or contact your insurance company to get a referral to someone in their network. Your preventive annual physical should be free - it is on most plans, to encourage people to get checked out before there is a problem. Do take advantage of it. Even if there is a charge, go anyway - it's always cheaper to take care of yourself when things seem good. And you are a young, overworked, single mom - if you don't look out for yourself, who will? Promise yourself that you will make this call next week no matter how hectic your life seems.