Not good at dating, flirting, or anything really.

22yo male, I've been in 2 relationships but both of them have been long-term, 1st being 5 years and 2nd being 2 years. My ex and I just recently broke up a couple of months ago due to the fact that I was going to be re-enlisting into the Army, although there was other reasons for the breakup that was the main one. Well the army was a bust and her and I work at the same place, when covid-19 hit her parents wouldnt allow her to work so I told her she could stay with me and my 2 roommates so she could continue to work. We have both already agreed that we will not be getting back together. I don't know for sure if she still has feelings for me but I know I don't with her and I am wanting to move on. I have a friend at work who I have pretty strong feelings for but I'm not good with flirting or anything really but I do know that she does like me as one of her friends told me. Her and I do flirt as we mess with eachother and I notice she always likes to bump into me when we're walking next to eachother and things like that, we've snapchatted eachother alittle bit here and there but the conversation normally ends up with one of us not replying. I cant blame her for not replying as im not the greatest at responding or I overthink things like if she sent a short reply then I just assume she isnt interested in conversing so I just don't reply, thats just my anxiety I guess. Shes really sweet and she always cheers me up and makes me smile, I constantly think about her and I would like to ask her out but there are several reasons why I cant bring my self to asking, like: I LIVE WITH MY EX…… We work together, I'm scared (What if she dosnt have the same feelings and rejects me and now our friendship is ruined) She smokes marijuana I don't (I always tend to see most girls who smoke look for guys who do, idk maybe im just making up excuses) (Also I don't really have a problem with her smoking) Idk im just not good at dating and im just looking for advice I guess. In the end I guess ultimately I'm just scared, scared of rejection, scared of losing a friend, scared of getting hurt.