Not TTC related - Old work problems

My old job under paid me by about $3 an hour every paycheque for two years. I only found out about 3 months before I quit. I have been talking to my old Union about it since I found out and now since I haven't worked there for about 4 months I get a settlement offer of $2000. I am so pissed because that works out to about $0.52 per hour extra which is not even close to what I should be getting. I'm so mad that my union would even consider $2000 as an acceptable amount.