Unfortunately, you are dealing with what most parents deal with when first doing CIO. i can tell you didn't read the Ferber book, and are just letting your baby cry. Although we all call lit CIO, really, it's not that harsh.
You should put your child to bed, after doing the night routine, and leave for a set time period. I started with 3 min.
after 3 min of vigorous crying (not whining), go in, reassure him, and leave. this time, wait 5 min.
if after 5 min he is still crying, go in. reassure him (NO picking up) and leave within a min.
This time wait 10. go in after 10, same reassurance, and leave.
Until he sleeps, go in after every 10 min of vigorous crying. remember whining and quieting down are what you want at first, to teach your child to put himself to sleep.
Then, night 2, you start at 5 min, and work in intervals to 15.
this goes on, increasing each night until you don't need it.
6 months is a bit early do try this, but it has worked out for many parents at this age.
best of luck, and really, I highly suggest getting the book Solve Your Child's Sleep Problems. it helps so much to understand WHY this works and also how a child's sleep patterns vary drastiadly from an adults.
HOPE THIS HELPED!