Dating

Is it only sex with this girl?

I started a new job about 4 weeks ago. Two days after I started, a girl that has worked there came in and said she just broke up with her boyfriend. Two weeks later we hook up after going out with some coworkers. I have been at her apartment every night after work now for about 3 weeks. I think I've only been at home for about 3 days out of 3 weeks. We have sex constantly and have only been on one actual date during which we had sex. She's been giving me some strange feelings about being used and leading me on. Several of my friends have noticed it too and have mentioned about me being just a rebound. A couple Friday's ago, I was supposed to go over to her place and hang out but ended up staying home and she got very upset with me. At this time I had only been seeing this girl for about a week and it made me feel weird that she got upset so easily. I'm not sure if she's just using me for sex or if it is leading somewhere. I've stayed the night a few times but not very much. It just seems like we had a one night stand and now we're seeing each other all the time. We don't message very much when we're not together and we see each other at work every day and have lunch together often. Also, is this something that I should maybe slow down with? I feel like she's leading me on and using me but am I also contributing to that by not telling her we need to slow down?
Is it only sex with this girl?
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