Is this heartburn or indigestion?

I know that sounds dumb, but I've never actually had either. I have had a slight warm or acidic feeling in my lower esophogus since yesterday morning. I didn't eat anything abnormal, but I did have too much to eat the night before it came on. I had plenty of water and a cup of tea before bed. I felt thirsty but very full. When I woke up, instead of feeling better like I do on the occasions that his happens, I felt like I had to burp but couldn't, and when I lay down and/or roll over, I can usually feel the "heat" rolling with me. The burp feeling hasn't really gone away either. It's not constant, and the intensity varies.

I am 35 weeks pregnant, and I know heartburn is a common 3rd trimester symptom. I'm just wondering if this is it or something more like indigestion. I had some icecream last night and it helped a little. Milk with breakfast has minimal effect. I'm trying to stay upright, but when I feel things moving I might burp, more often than not nothing happens.