Learning Italian....

I have been living in Italy for 9 months with my Italian girlfriend who speaks Italian and English. I only know english and to be honest have no recollection of how I learned that. At first I was excited about learning Italian and it appeared easy and logical. Then these "Irregular Verbs" appear, which aren't that irregular at all!! All of a sudden for one verb I have to memorize around 20 different mutations!! And after the novelty has worn off and you have to get down to business it is extremely boring to learn another language, I mean look in a dictionary and memorize words. I actually start getting drowsy after 5 minutes and fall asleep.
My girlfriend and I always try to start only speaking Italian in the house but after around 15 minutes we unconsciously revert back to english. Don't get me wrong I do understand quiet a bit of Italian, I can read Italian much better than understanding someone speak it. Thats another thing, some people I can understand 75% of what they say but others I don't have a hope. Italian is a beautiful language but it all sounds like one long word because it flows so smoothly.
When I try to understand people talking I try to translate it in my head into english, comprehend it, then find the words in Italian for a response but I think this mental procedure is taking to long and it is either because I am stupid or I'm learning it the wrong way. By the time I have finished translating the first sentence they are on their seventh sentence and I have missed everything in the middle I used to have a Brazilian friend who didn't know much English and used to tell me I spoke to fast and I could never speak slowly enough for them and couldn't understand, Now I Do!!!
Anyway, if anyone knows the average time it should take to learn Italian. Is there anyone who has/had the same problems? I was so cocky before I left country that I would learn it easy in 3 or 6 months tops