Help Us! R we doing something WRONG?!

My husband and I are trying to conceived this month. We wanted twins but don't have the funds for the services or procedures that's needed. We would try using the fertility pills but never heard of anyone who took them that conceived twins. At this point each month during my fertile week according to this app and 2 others I use we have had sex. Yet we never do it the day I ovulate should I just do it on my ovulation date or the entire week? I was recently on birth control (the patch) but took it off after a week of having it because it was non-stop nausea, vomiting and headaches (I hated it). Any suggestions ladies? help us

ps Only reason I want to be pregnant this month is because he's the only August bday so I feel we need August baby or very close to it.

the rest of us are winter babies