Was it Preterm labor?

Friday evening I had just gotten home from work and hubby and I were cuddling in bed relaxing after a long day before starting dinner, we were kissing and one thing led to another and we started having sex, I was on top and right when things were getting hot and steamy I felt a gush of fluid and I know I didn't finish so I thought I peed on him, we turned on the lights to get a towel and it was a lot of clear fluid mixed with blood, some of the blood mixed with the fluid was pink on the sheets but when I wiped it was very bright red! we showered and called the night nurse for our doctor and we were advised to go to labor and delivery just in case it was the water breaking. We get to labor and delivery and get checked in and tell the nurse what happened and she does an exam checking inside with her hand, she pulls her hand out and said " well it's definitely a bloody show" and notifies me that my cervix is extremely soft and starting to open. She hooks me up to the monitor and says we are going to do a non stress test for 20 minutes to check for contractions and leaves, at this point I don't feel anything just the baby moving like normal. She then comes back with a bottle of terbutaline and says I'm having lots of small contractions and that I need a shot of this to stop them and "calm down my uterus" and that I can have up to 3 shots and if it doesn't work they will need to admit me to do an IV for fluids and other medications they can try that they are trying to determine how aggressive they need to be with all of this. At this point I don't even know what "this" is and I ask her if my water broke she says she is still unsure. So I receive my first shot and with in a minute I feel jittery and my heart is racing. She says it's a normal side effect and after a second shot and about an hour later the ultrasound tech comes in to check and see how the baby is doing and to check the fluid and the size of my cervix. The nurse comes back in after the tech leaves and says that the contractions have stopped and my cervix is 5cm long so I'm okay to go home but I must stay on bed rest all weekend because my cervix is extremely soft and starting to open and that I must go straight to my doctor Monday morning and not wait for my appt on Thursday. I asked her so what do I make of all this? And she said "sometimes this just happens, but the baby looks great, blah blah blah not really a straight answer, she never clearly stated what was going on. So what was the medication for was I in preterm labor or what's going on? Why is my cervix so soft and is it dangerous that it's starting to open? I see my doctor tomorrow but I would like to know your opinions and advice! Thanks!!