For the first 3 months after converting to Islam I did not pray as I lived with my parents and did not want to upset them by praying in their presence. Do I need to make up for prayers before I accepted Islam and for the first 3 months after converting?
Bismihi ta'ala
There must have been many things you had to deal with when you first converted to Islam. This is very common, and you should take things on a normal pace so you familiarise yourself with the precepts of this new religion you have adopted.
As for praying, there could have been alternative options, where you could have avoided upsetting your parents, and also observe your daily prayers. Like, praying in closed off area, or bedroom, etc.
What you can do in your free time and gradually pray these days, as qadha`, or as re-doing that which was obligatory for you which you missed out on. See it as a blessing, as when we pray, although more than our daily routine, that is indeed an honourable blessing from the Almighty, as there is nothing better than worshipping Him.
With prayers for your success.