I too had one who wouldn't readily take a bottle. We spent LOTS on nipples. The even flo was one that she finally took. As she got older she got less finicky about nipples.
I don't know that nipple confusion will be much of an issue given your child's age. I think it tends to happen - if it does- most often when children are give bottles and pacifiers early on - before they have established good solid breastfeeding.
I don't know how long you need to be away from your child to work or how often your child nurses BUT I do know a couple of people who returned to work whose children wouldn't take a bottle. Several of those kids would just 'wait it out' - and they didn't starve to death or anything (but their moms weren't away for 10 or more hours - they would go for 6 or so hours)
If you want to continue breastfeeding maybe you can work out an arrangement to nurse in the middle of your shift- having the baby brought to mom has worked for some. I went to my child's day care at noon every day and nurses.