Anyone given birth prematurely in second trimester recently?

If so how many weeks were you? What made you realize you were in labor? How did the contractions feel like? Was there any vaginal discharge out of the ordinary? How long did you wait before going to the hospital?

I am 23w3d today, and I have had 2 scares this week. First, some half inch thing fell out of me on Sunday, which I still don't know what it was. But because I didn't have any pain or bleeding immediately following it, I didn't give it much thought the next day. Then today, for 3 hours atleast, I had back pain, feeling of nausea, and my stomach felt super tight and uncomfortable. Also there was a lot of pressure on my pelvis and it felt very heavy. I don't know if they were contractions or just the baby stubbornly laying down in my pelvis, but the whole time I was feeling her kicks near the middle. I still have that heavy feeling in my pelvis 6 hours later.

I just want some information from moms who have actually given birth prematurely so I can know what to look out for.

Thanks!