my ex and the new guy

so my ex and i were together for like 25 yrs and we split a few months back. been single ever since but recently this hot neighbor guy started messaging me on fb. he's in his early thirties, fit, really attractive. we've hung out a couple times already, just dinner or drinks. tonight we got kinda drunk at this bar and ended up going to my place cuz it was late. he told me how much he wanted me but i was still so unsure about jumping into something new after being with one person for so long. finally decided fuck it, went ahead with him anyway. the sex was incredible, first time in a while too. felt really good getting off with someone else besides my ex. but afterwards, couldn't help feeling a bit guilty and weirded out. just not sure if this is normal to feel like that after so long being monogamous. what do you think? anyone been through something similar?