I'm in the middle of a sewing class right now and learned two things about thread.
1. Use high quality thread. Check for fuzzies on the spool, if the spool looks fuzzy that means it was made using shorter fibers which can cause more tangling and breaking.
2. Thread can get bruised. Think of it like dropping an apple. Try pulling a good amount off the spool and try again.
Oh and don't forget thread ages so if its older than 3 or 4 years old...throw it out.
BTW love the shirt!!!