The 36-year-old tennis pro covers InStyle's August issue, the magazine's first-ever "Bada** Women" issue, where she opens up about possibly expanding her family with her husband, Alexis Ohanian, and their 9-month-old daughter, Alexis Olympia, and whether becoming a mother of two would ultimately be the cause of her retirement.

"If I weren't working, I'd already be pregnant," admits Williams, who withdrew from the French Open earlier this month due to a chest muscle injury. "I don’t know if I want to play if I have another baby…"

Williams adds that finding out she was pregnant with baby Alexis during the Australian Open last year was not easy, and returning to the court five months after giving birth was just as difficult.

"I had a really tough first round and an even tougher second round," she recalls. "I thought, 'I'm probably going to lose early. That's OK. I have a good excuse for the first time.'"

"[After birth I was] in the locker room pumping before a match because my boobs are so big," she continues. "When I pump, they go down a size or two and I go out and play."

Back in March, Williams told ET that she would "definitely" like to have another child with Ohanian when we caught up with her at the 14th Annual Desert Smash Celebrity Tennis Event in La Quinta, California.

"I definitely want two [kids], God willing," she said at the time. "But right now, I want tennis as well. So, I'm going to wait and see what happens."

"It's definitely not easy," she added. "I have this undying drive to be the best that I can be. Whether it's [being] a mom or playing tennis or doing my designing. I just want to do the best that I can."