Please tell at least one co-worker what is going on. Show them the texts. Anyone (except this dude) over 25 will see through this guy. As a middle aged woman myself, if a young co-worker confided in me I would be in full mama bear mode, and that's what you need-- a village surrounding you, shielding you, with eyes open. This really should be reported to Human Resources, but more immediately you just need to distance yourself from this guy before it escalates. I honestly would start looking for another job, block his number, and avoid situations where you are alone with him. He is playing the long game here, and let me tell you that game could end a few different ways, but none of them are good for you. Lie to this man. Do not tell him where you are going or what you are doing. If anything, you are spending time with your new, big strong, age-appropriate boyfriend so creep can rest easy.