help!

Ok so my husband and I are trying to conceive and we are having a hard time. I check my bbt every morning before getting out of bed, take prenatals like the Dr said to do when trying to conceive, eat right etc. What will/should bbt be when ovulating? I have very irregular periods and sometimes I just spot for like 2 weeks only when I use the restroom so it's hard for me to just go by my cycle predict when I will ovulate. So any tips you lovely ladies have, send them my way :)