Performance anxiety?

Interesting query. Am 22, have been sexually active for 6 years. Have never had any problems with getting it up, keeping it up, to the contrary the wind blows the wrong way and I'm ready to rock, and almost always last a long time or sometimes too long and have been freakin' proud of it!. I recently got out of a 2 year relationship and have acquired a new boo I guess you could say...this is my 6th partner and I don't know if it's performance anxiety or what but I have trouble keeping an erection. BAM its up and then as soon as the sex is about to begin I lose my erection. I'm a little crazy and so is my partner so we're both really awkward sometimes and I know that's part of it because in the back of my mind I'm overanalyzing everything....failing that though what exactly is the matter? We have had really great sex a couple times and then some mediocre sex several times where I came in a couple of minutes, and then a few totally f&*# devastating attempts at sex where the aforementioned deflation happens. WTF is the deal? My only ideas are the new partner bit (which has never bothered before) *or/along with* the fact that it s someone new after having an exclusive lovey dovey partner for 2 years? The relationship ended on a good not and I'm definitely baggage free etc but am I conditioned to be having been turned on in certain ways and am just going to have to acclimate myself to a new partner? Never bothered me in the past tho!

Definitely freaking out here, trying to do something about this before I strike out which I absolutely do not want to :/ Any questions I'll be more than welcome to answer them!!!

Thanks in advance to whomever can help! And thanks to the gods for the interweb, where this kind of thing can be discussed in (relative) anonymity.