Couldn't read and not reply either
I was in your shoes a while back. We had an 'open adoption' but my adoptive parents didn't like the idea of me having contact with my birthmom, so they didn't help anything and made it weird. I had nagging feelings like you described, and when I turned 18 I did go visit and talk to her on the phone. My adoptive parents weren't supportive, but they got over it.
Now that it's been a bunch of years and I have my own family, I keep my two 'families' separate (adoptive and birth). When my adoptive parents visit I'll even take the pictures of my birth family off the wall
just too much complication there. I do love talking on the phone with my birth mom. She calls me her daughter, and that's fine with me. I call her by her first name. I do call my sisters my sisters, no 'half' or anything. We enjoy talking about how we're similar, and seeing similarities with the men we've married, what foods we like, etc. I tend to think of her more like a 'hip aunt' than my *mom* I don't know, *mom* seems to be a little to... loaded? Pressuring? I don't know.
At first I mostly wrote letters because I wasn't good on the phone either. I've visited her 3 times, twice when I was single, once when hubby and I passed through that state on the way to somewhere else. I also backed off if I felt weird. There was a whole 6 months or so that I didn't have time to write or call around the time I married my husband. I was still kind of awkward about our relationship and didn't want to tell her that I was getting married because I didn't want pressure to invite her to the wedding (that would have made it SUPER awkward with how my adoptive family is), so I just didn't deal with it. If any 'emotional balls' so to speak have to get dropped, it's the biologic family who gets dropped soonest.
That's just how I've done things. We get along super well, we're really similar. I enjoy talking to her on the phone, and she and her husband are most likely going to come up and visit us this spring or summer.
don't know if that helps