Honey, there is more in your life to focus on than this boy.
To start with, if you have not yet gotten your period then you MUST get a pregnancy test just to make sure that you did not get pregnant.
I know you said you used protection, but protection is not infallible and accidents CAN happen.
You can purchase an at-home test or go to Planned Parenthood to get tested (they will not inform your parents).
Next, your zodiac signs have very little to do with this situation. I know you want to believe that they play a major part in the success or failure of relationships, but at this stage of your life the role they play is very minimal.
At this point, the factor which most influences the success of a relationship is the two people involved in it.
Here's what I think:
~ You are too young to focus on one boy. At 13, the maturity level between you and a 15 year old is an ocean apart.
~ Your relationship with your parents is important. Lying and sneaking in order to get what you want will only lead to more trouble and a lack of trust.
~ Thirteen is very young to be having sex. Even with protection, the possibility of pregnancy exists. Very few teens your age (and his) are ready to be parents.
~ You already lied to this boy about your period in an attempt to keep him. Relationships based on lies are never successful. Trust is an important foundation of any relationship, and you have already shown that you are willing to overlook it.
Hon, you were only with this boy for a month. But from what I can tell from what you wrote, he sounds like a pretty good guy. What he has done (and told you) is the right thing.
I know you don't want to hear it, but it's the truth.
This does not mean that the two of you may not get together later on in life, but now is not that time.