Is it me or the bike? I'm a tri bike flunky!
Ok ladies, I really need your help/advice about my tri bike.
Brief history: I started out riding on a Trek 1500 WSD bike years ago. I love her. I'm dialed in to a perfect fit and am very comfortable on her at any speed, on any terrain: hills, corners, etc. Today I rode 52 miles, averaged 18 mph, and hit speeds of 24 mph several times on flat terrain racing friends.
A year ago, while training for IM Louisville, I purchased a Cervelo P2. It's supposed to be "da bomb" of tri bikes, right?
Is it possible to just not click with a bike? 
I've had 2 professional bike fits on the Cervelo. When I bought it, I was F.I.S.T. fit to it -- and thought I was just "mental" about the instability I felt because I was switching from the road bike to a tri.
The LBS fixed a few things with my fit, told me I'd need an adjustment period to get used to riding much more aggressively and sent me on my way. I had a crappy IM bike split -- would've been much more comfortable/faster on my cheaper, heavier Trek.
I spent all winter riding the tri bike on the trainer, still trying to get used to it. I had a second bike fit with a different LBS about 250 miles ago on the Cervelo.
They spent 2 days with me, measuring everything on and off the bike. They changed out my stem for a longer stem, lowered my seat, lowered by bars and widened my aero bars. It felt OK on the trainer but in practice -- it's not a lot better.
I still hate the Cervelo. Highly dislike it. I still don't feel comfortable, and I'm actually slower (much) on it than my Trek. I had it out for 40 miles this week and my average speed was 14.9 mph. 
Is it possible it's just not a good bike for me? My husband and 2 of my training partners have various models of Cervelo and looooooveeee them. No one seems to understand why I don't like mine.
How long does it take to "get used" to a tri bike? I'm going on my second season and roughly 1700 miles.
“Some people want it to happen, some wish it would happen, others make it happen.” - Michael Jordan