Fourth Attempt - GMAT 620 (Q44, V31)

Hi,

I gave my GMAT on 19th June, and scored a 620 (Q44, V31). I seriously don't know if i should be happy or sad, since this was my fourth attempt. The history of my earlier scores is as follows.

First Attempt : 470 (don't remember the break up)
Second Attempt: 570
Third Attempt: 570
Fourth Attempt: 620 (Q44, V31)

I was averaging 650-680 in all my practice tests, and so i was expecting at least a 650. I felt happy in one way, cause i was struggling even to cross 600 and a lot of schools require a minimum 600 score. But also, I know a 620 score is not something to be proud of and I am still on border line. I have read alot of blogs and forum , and everyone says that retake the GMAT, and score around 650's. However, I am not sure if a 5th attempt would be a good idea?

Please advice me on the following:

1. Should i give a 5th attempt? Will it impact the way schools evaluate my profile?

2. My Profile is : 4.5 years work experience in consulting field. GPA 3.3. Masters in Accountancy.
I am aiming for schools like NUS, Warwick, HKU, Nanyang and Imperial college. What are my chances?

3. If I am not eligible for the above schools. Can someone please recommend me some universities, which i can apply to with the above gmat score.

Kindly help me out, I am really confused and feeling helpless. I don't want to retake GMAT, at the same time, I want to get into any top 50 universities.