ok this is what I know but am no expert
your CM is cervix mucus this is the liquid you will fill and will sometimes come out on your finger if you examine yourself, this changes through the month as follows:
Before Ovulation (low chance of pregnancy):
The first few days following AF there will be little or no CM present. You will feel dryness
Approaching Ovulation (chance of pregnancy):
The first CM that appears should be moist or sticky and should be white or cream in colour. if you have it on your finger You will only be able to pull your fingers about 1 cm apart before it breaks.
Right around ovulation (high chance of pregnancy):
At this stage, cm resembles egg whites. It is the thinnest, clearest and most abundant at this point in the cycle. if you have some on your finger the the mucus can stretch quite a way (several centimetres) before it breaks (if it breaks at all). ) The amount of this thin mucus will steadily increase until you experience your 'mucus peak'. This is the last day of this period where the chance of conception is high. It is closely tied to ovulation. During this phase, the sperm's survival rate is higher. It can survive in cervical mucus for up to 72 hours, a significantly longer time than during the rest of the cycle.
After Ovulation (low chance of pregnancy):
After ovulation, there is a marked change in CM appearance. It returns to the sticky stage (does not stretch during finger test).
I always check mine and it is such a good way of testing and its free
with your cervix position this is slightly different for each women I for instance can feel mine all the time sometimes its so low its only just at the entrance and other women find it hard even to reach it! but these are the outlines -
Prior to ovulation - during the first half of your cycle, the cervix will feel relatively firm (like touching your nose) and dry to the touch - and the position of the cervix will be low in your vagina (easy to reach). The entrance of the cervix will feel closed.
However, as you approach ovulation, the cervix will become increasingly soft and will increasingly moisten in order to create a more fertile environment for the sperm. The entrance of the cervix will feel open and begin to lift. At the highest point, the cervix may be a bit difficult to reach and the entrance of the cervix will increase in size. The feel of your cervix will be softer - like touching your lip. At this point, you are at your most fertile time.
Following ovulation, the cervix begins to return to a firmer state and the entrance will begin to close. Also, the position of the cervix will again drop and become easy to reach.
Then your are PG your cervix rises up and becomes soft but this sometimes doesn't happen for a few weeks after you become pregnant
Right hope that helps any Q please just ask