Supply fear when returning to work

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This is a long post lol I’m currently in my third trimester and im trying to have a plan for pumping ahead of time since I’m new to it. I am worrying about how I will pump when I go back to work..my plan is to pump to get a stash going and for bottles but to also breastfeed as well. My worry is that when I go back to work, my supply will diminish. I know a lot of people who go back to work have the options to pump during a lunch or multiple designated times but my workplace isn’t really suited for stopping multiple times a day to pump. I’m a mail carrier so its hectic and we are only in the building for a few hours before we go to the street to deliver. During those few hours I have to sort and organize mail and packages. I’m afraid that in a shift, I’ll only be able to pump 1 time during a lunch. For example: my shift would be 7:30am-5:30pm..somedays I may be done sooner or some I may work later. I would make sure to pump before going into work. I would have to pump again sometime before 10am and store in a work fridge because I’m usually out on the road driving after that sometime..if I’m making good time, i “might” be able to stop and pump on the road if I have a good cooler with me that I could store it in but it’s not likely that I’ll be able to do that. Therefore, I wouldn’t be able to pump again until I’m off work which could be up to 7 or so hours after my last pump..I would obviously pump after getting home but I’m afraid my supply will go down because of extended periods of time without pumping..this would also be 5-6 days a week..I’m also afraid that my breasts will become very sore from the long wait (does that happen? FTM over here lol). Any advice from people who have a difficult work setting for pumping?