My DH and I would like to start trying for baby number two...

My cycle is between 33 and 38 days so I would like to take my temp to determine when I ovulate as I'm pretty irregular. (I did this with baby No. 1 and it worked like a charm)...However, No.1 wakes for a BF between 4.30 and 5.30 every morning? So I'm not sure if taking my temp is going to be accurate, as last time I was told to take it at the same time every morning not before 5am... does anyone have any suggestions on what I can do????