When deciding the best time to start trying, I would look at the time in my life rather than the time of the month.
There has been a lot of research regarding a child's development when born into a home where the parents are married and those who are not married. It benefits the child to live in a situation where the parents are married to each other.
It sounds to me that you and your bf love each other a lot (why would you want a baby), so why not consider marriage for your own good and for the good of your child?
Sure, the two of you could just live together (you may already be), but there is no substitute to the commitment of marriage.
I guess if it were me, I would want to give my child the best. I would ask myself what kind of a situation I would like to be born into and try to create that situation for my child.
I will always be grateful to my parents. They waited to get married until my dad had finished his doctorate to start trying for children. That way both my mom and my dad could give me and my sister their full attention and they could provide for us financially. That was such unselfish love! My parents put the needs of my sister and me above their own wants to have a child.
Waiting for marriage is a good choice for you and your future children and something that I do not think you would regret.