Ex moved on with new girl but still keeps tabs on me. Possible stalker?

So long story short, my ex dumped me almost 4 months ago. Things got really bitter after we had went through a miscarriage, and he ended things with "I'm still in love with you, I just can't do a relationship with you". In the past he has made up elaborate lies about having gotten another girl pregnant and being engaged to her, he only stopped trying to convince me of this when he found out I was pregnant. He goes through a bunch of drama after this, blocking me on facebook and social media. In attempt to get over him faster, I started hanging out and eventually dating this other guy the next month. Within a week of my new relationship, he messages the guy and tries to extort me in order for him to break up with me. I found this odd, as he had blocked me through media and still tried to keep tabs on me. A few weeks later, he moves on with some girl that he was friends with in our relationship. They go nuts on facebook, posting pictures together and calls her his fiance. It's the same thing as the last charade, but I try to let it go. I check up on him sometimes because it still hurts and I am not fully over him at that point. It seems like he parrots my moves with my boyfriend. Everytime I post a picture of us, shortly after he has one of him and her up. If I change my profile to a photo of me and my boyfriend, he does the same thing a few days later. A few weeks ago, I was looking up one of my meme pages on facebook and his account popped up under the list of pages. I was shocked at first, seeing him unblock me out of the blue, but I didn't think too much about it. Later that day I go to work and he shows up there with his new girlfriend. They end up fondling each other and kissing each other in front of me. When he approaches me, he acts as if he doesn't know me. I don't know why he would even bother going through all of this. What could he possibly be trying to attempt here, and do I need to worry about my safety soon?
Ex moved on with new girl but still keeps tabs on me. Possible stalker?
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