I feel like a terrible aunt... please help

My niece is almost 4 years old. I am raising her (partially) myself. Her mother hasn’t been around for well over a year now, but her dad (my brother in law) is. But he works the same job as my husband and the can work from 6am-anywhere from 6pm to full overnights on rigs. He’s super young, so even the days he does get off work at decent times about half of those times he still doesn’t come to get her, sometimes he asks and sometimes he lies about when Hes done working. That’s just a fact of the relationship we have caught him lying about pointless things so that he doesn’t have to come get her even tho he will complain he never has time with her. So essentially I’m the one raising her about 3/4 of the time alone. My issue that I need help with is, since this started and I became a parent rather than an aunt role because she needed it, I feel like maybe we have lost our special connection. I’m doing discipline, chores, school work, gymnastics with her rather than just playing and hanging out. We try to keep a solid schedule because she needs the schedule to help her out. I feel like I’m more of an authoritarian and schedule keeper with her. I’ve been so irritated with her lately, sometimes when she’s done nothing, and I can’t remember the last time that we cuddled together honestly. I feel bad. I’m also almost 22 weeks pregnant right now with my angel baby. Is it just my hormones? Is this just how different it feels to be the parent rather than the aunt? I’m so confused. She doesn’t seem bothered at all by the difference. Please help! What can I do? And why do I feel like this the past few months?? 😫😫😫