Itunes 12.3.1 not responding on 10.10.5

I can not get iTunes to work. When i start it up first time, it takes about 45 mins for the browser window to pop up, then just the spinning wheel until i quit the program. I've left it open for 5 hours and still nothing. I have a pretty large library and i have also tried deleting iTunes and re-installing it. Still nothing. Also, all my music is on an external hard drive, but the HD seems Ok and is mounted on my desktop. Not really sure what to try here. Any advice would be most appreciated. Also, this just started with the new version, although i did notice it running slower on the last version but i could play and listen to music.

thanks