Is my SSD drive faulty when Blackmagic disk speed test shows decreasing write speed as low as 10 Mb/s? I have old plastic white MacBook 13'' 2007 mid late.

In previous year I have bought SSD and replaced old one (HDD).

Everything was Ok, but in last month i started seen how sometime OS become stuck for one-two second, and then everything is ok.

Today I have download 


  Blackmagic Disk Speed Test


And it shows me good speed, but only at once. Seems to me it is testing my drive in cycle. It trying to write then read, then repeat cycle. So in first try it shows nice digits as a result, but then "write" (and only write) numbers become lower and lower, and fixing about 10 Mb/s. Is it mean that something non good with my SSD drive?
mapasov pointed this link out for me to enable TRIM if you're using Lion http://digitaldj.net/2011/07/21/trim-enabler-for-lion/

It means that your system will handle TRIM as if it were a native Apple SSD, and that you shouldn't get the problem you're facing after the system has had time to manage it