Yes, do request feedback as Elqyn said. 7/8 have rejected you without interview which can be a result of 2 possibilities: 1) your grades/test scores/PS/ref aren't good enough or b) you havent applied wisely and to your strengths. Looking at your profile your ukcat scores seems fine, they are much much better than me. Your academics, although not the strongest, are definitely not bad.
This leads me to believe that the culprit is either your PS or you picked the wrong schools.
I'll ignore last year for now. This year with a 680 ukcat, and your academics should have been good to go for an interview for an offer with Southampton. But here's the kicker...Southampton bases offers 100% on PS and reference. They only use academics + scores to see if you meet cutoffs. The fact that Soton did not give you an offer both years leads me to believe that your PS is a major issue.
Newcastle is really hard school to get into but the fact that you managed an interview means that your application is certainly strong and they dont playce 100% emphasis on PS like Soton, so you managed an interview. But you were rejected after which can be two possibilities: bad performance or too much competition. At this point, I think your rejection was a mix of both...Newcastle is definitely a hard school to get into, and perhaps your interview might not have been the greatest.
With all this in mind, if you do decide to apply next year, please work harder on your PS. Get another reference (preferably better). Research all schools once again and apply only to those that cater to your strengths. Hope you are successful at some point, I wouldn't suggest giving up after 2 tries...
Good luck