Did I blow my chances of getting the job?

I went on a 1 part interview which went well - the employer said they would make a decision by end of week or next week and I sent a Thank You email same day. So Thursday rolled around and I still haven't heard anything yet, so I decided to send a follow up email expressing continued interest in the position (I was kind of unsure whether I should send it because I didn't want to seem desperate). Well as it turns out, I got a call on Friday from the employer telling me that they wanted me to come in for a 2nd interview on Monday morning. At first they said it was a 1 interview process, but now it's a 2 part interview. So I came in and they asked a few more questions and told me that they were having their candidates take a assessment test. I've never had to for what I do, but I was sure that I would do fine. I did ask how many candidates are in the running for this 2nd round and I also asked by when were they intent on making a decision. They told me by Wed or Thurs, because they want someone in there very soon. When I got home I sent another Thank You email. Well Wed came and went, and I was sure that I would get a call back with either yay or nay on THursday... 4:30 rolls around and I'm in suspense because I still haven't heard anything yet. So I decided to call them to find out where they were in their decision and to politely inform them that they said a decision would be made on Thursday and that I have been interviewing and was actually extended an offer earlier today. I told them that I didn't want to make a decision just yet because I'm more interested in this opportunity and wanted to hear back from them first. All in all the person I spoke with said they were still making a decision and calling references. Should I not have told them that I was extended an offer? My references haven't mentioned to me that anyone called. Did I blow it? I should hear back something tomorrow. Feedback is appreciated.....uuugghh....