HI, I just finished my 1st year of PhD and I am realizing that my PI doesn't have best interests for me.
Before I started my PhD i volunteered to work on a project for him for 5 months before he offered me a project coordinator position & convinced me and I would get funding once I started my PhD and it could become my thesis. The first 8 months were fine. Then in the fall when I was going to start my program, I was supposed to work as a 50% RA and I had signed the contract. Couple months later, he asked me if my workload was a bit too much we could hire another RA and i could be 25% RA, however, one of our RAs who was already on the project told me she could help me instead (and we discussed with my PI), I could stay at 50%. Within a month, I checked my bank account and realized I was getting paid as a 25% RA. My grants manager told me that he had pulled me down to 25% within a week after I had signed the contract. When I brought this up to my PI ,after much hesitation, he pulled me back to 50% & also reimbursed me for the work I did as a 50% RA (as I had continued to work 20hrs per week since I had no idea about this). I let this go as a misunderstanding.
At a recent conference, I made a contact with an european scientist and we are not collaborating on a study. He wanted me to come to his city to visit as well as learn about the public health system there and requested to my PI that he would like me to come. My PI tells the European scientist that we don't have grant money (even though my grants manager told me we have enough money for a round-trip ticket). The European scientist emailed me to tell me that he would still like me to visit and if i can just buy my own ticket, he would take care of my room & board. But I am not even sure if I can go until next summer. Now another opportunity presented itself where a phd student requested my PI that i go to one of the South East Asian countries to collect data. Timeline wasn't working out and I talked with the student that I can go next May. She ends up choosing my colleague who has same PI as mine and didn't have funds to go that country for her own project & she's going in April. I have a strong feeling that my PI has a role in this as he's the PI of my colleague and often gives preferential treatment to her over me. These are just couple of examples, ofcourse, there's more.

He puts so much work on me that my grades suffered and yet I don't get much positive feedback, he puts me on the spot in front of other student(s), criticizes me, which humiliates me. He would rather let the study suffer than talk with some of our RAs who were slacking on data collection and the workload falls on me. I am so tired I want to quit and am losing motivation & am starting to hate my project. My confidence is in the dumps & I don't know how to build a thick skin to deal with these politics and criticisms. Are all these feelings normal among PhD students? How do you deal with them? Plz share your story.

sorry to hear your troubles. I have recently completed my PhD and also did not have a supervisor that was "supportive".  Yes, these feelings are normal! Yes, you must develop a thick skin! Its not easy but you will get there in the end! Do not ever believe the PI has your best interests at heart....sometimes they are just out of their depth (Inexperience(!?)/poor project managers (alot of academics!) or do not think for whatever reason of the students best interest). You must concentrate on yourself and work out how exactly you are going to finish this phd. Personally what got me to the finish line was " I've started so I'll finish". PhD is hard as its a mental marathon with many ups and downs. Personally, my self-confidence was rubbish the whole way through my PhD. Following the write-up I could have taken on any expert in the field (which you do obviously in your viva) and passed great. What I'm trying to say is ignore your PI, do your reading and experiments and increased confidence will come with time and experience.Good luck! You may feel differently a year from now! Your PI seems a little "awkward" so I would personally make sure I was extremly pedantic as I went about my work keeping records of emails, writing up the outcome of meetings for my own records etc etc