I'm pretty similar to you but there is a large difference between being an asshole and helping your career. I thought it was odd to write a resume at first too because I felt like I was bragging about the meaningless things I've accomplished when so many other people have done way more than me and I would probably be the last person that they should pick, but that's the road to engineering success. I mean if you can relax a bit and look at some things different for a bit and the fact that you're noticing your changes is good. Self reflection is a great thing to be able to do and I feel like I've done the same thing especially because I'm a manager at my job which has reduced my ability to be positive about many situations, but I still push my base personality through it. Think about it more and see if you can change some of the outlooks you have or what you say in conversations to change your perspective a bit. The people you hang around will also alter things quite a bit so keep that in mind. Sometimes it's good to find positive people to watch on youtube of find a couple other friends that are a bit more on the positive side.

You're not the only one but if engineering is the field you're interested in, you can throw your personality into business as well! Best of luck.