Hi Scott @scott4
I’m not sure what a “C A 2” is, but if it is a tuning device and it shows that what you are playing / bending is several cents below what is shown when you simply draw without trying to bend, then yes, you are beginning to get a bend. 
OK, I think there are several issues to address here. I assume that you are talking about a harp that is in the key of Bb (B flat). If so, then you should study the following important chart closely and either store it on your computer or telephone or write it down:
This shows you, on the 2 lines that are yellow, the notes that are playable on a “standard” 10 hole Bb Richter harp without bending. As you see, -2 (2 draw) and +3 (3 blow) are the same note. (On harps that have a layout referred to as “Paddy Richter” this is not true; but I am assuming that your harp is not a Paddy Richter type of harp.)
For draw bends: They are only possible for the holes that have light blue boxes below them. The picture also indicates how many different bends are possible for each of these holes as well as the names of the notes that an accurate bend will be sounding.
For blow bends: They are only possible for the holes that have light red boxes above them. Blow bends are something that you should not yet worry about or try until you have learned to play draw bends confidently and consistently, and that will probably take much practice and patience. Remember the saying: Rome wasn’t built in day.
There are other types of bends (not shown in the picture) that are really tricky – even some professional harp players cannot play them well enough or with sufficient confidence and accuracy to use them in their recordings or concerts. Just to fill out your harp vocabulary: these other bends are the “overblow” bends and the “overdraw” bends.
Now back to your attempts to get draw bends: You say that you can get -4 and -5 to bend, but not very much. Well, look at the picture and notice that for hole 5 there is no draw bend. There is no note between -5 and +5 that you can aim for or play. The best that you can do is to hit what is often called a micro-tonal pitch. The videos on YouTube by Ronnie Shellist often have examples of him playing this -5 “bend”.
For -4 there is the very important (for blues music, at any rate) bend that you should continue to practice until you eventually master it. 
Keep practicing, using the chart and a tuning device or app and your skill will improve.
Regards,
– Slim 