could i be

hello everyone ok so i am 21 and i would like to have a child let me just get that out of the way. Ok so i am extremely irregular with my period sometimes i will cycles of 35 and other 28 is different every time. I do not use any type of birth control and only have one sex partner for over 3 years. For the past four months i have had a 35 day cycle so assuming i have another 35 day cycle this month i should get my period on september 4 to be exact. last period was July 31 till august 3. The last day of my period i had unprotected sex with my partner and he came inside me. On Saturday August 18 i started spotting early in the morning as i rushed to the washroom to pee. I had no cramping that day just minor discomfort on my right ovary (i do have folical cyst so that could be a reason for the bleeding).  The bleeding stopped on the 21. Then I had sex again on august 20 and once again he came inside me. If I am right I should have ovulated on the 21 of August. Three days after the last time i had sex my breast became a bit sore but not to the touch. I dont want to buy a pregnancy test since I have spend a lot of money on them already. I have a doctors appointment september 11 to check about the bleeding and the ovary pain so I would love any given advice as to could i be pregnant from having sex after my period or from august 20?