Dropbox Speeds Very Slow

Hi, I've been having serious issues with Dropbox... I use it regularly for work, and normally upload speeds aren't an issue, but for the past week I have been experiencing speeds around 1.5MB/sec. I was told by their support staff that I should contact my ISP to make sure that you aren't limiting my bandwidth when using that application? It sounds ridiculous to me... I've tried every suggestion they had to offer and they can't seem to figure out the issue, they claim it isn't on their end. As stupid as it sounds, I thought I should ask... is my speed being limited when using Dropbox? I do transfer terabytes worth of data a month, I'm not sure if it gets flagged or something? I shouldn't be getting bottlenecked though, right? I need to figure this out ASAP. I have gone through a laundry list of possible fixes, checked links in previous posts about this, spoken to their support several times, reinstalled Dropbox, disabled anti-virus and firewalls, restarted several times, reset the modem, ran troubleshooting, etc etc

Thanks