Not Null

I am writing a formula Rich Text field that is getting a bit complicated.  I am combining 4 text fields together, making the contents bold and italicized. 
Original formula:"<i><b>" & [CT - Q1 Comments] & "<br>" & [CT - Q2 Comments] & "<br>" & [CT - Q3 Comments] & "<br>" & [CT - Q4 Comments]

Then I saw when some of the comments are blank, there was extra space (I assume this is the breaks even though there is no text.  So I feel like I need to adjust the formula to contain nested If/And statements:
If [CT - Q1 Comments] = Blank and [CT - Q2 Comments], [CT - Q3 Comments], [CT - Q4 Comments] are Not Blank then "<i><b>" & [CT - Q2 Comments] & "<br>" & [CT - Q3 Comments] & "<br>" & [CT - Q4 Comments]

I believe this is going to end up being a pretty long formula since I would need to have every variation of each comment being blank.

I believe since these are text fields I would want [CT - Q1 Comments] = null however I don't know how to say [CT - Q2 Comments] Is not null.  I tried the not IsNull( ) but it didn't like that.

Any suggestions?