WASHINGTON — President Donald Trump isn’t a doctor. But he played one on TV Monday, offering copious amounts of unproven medical advice that he suggested — often without providing evidence — might help reduce autism rates. Trump repeatedly implored pregnant women to avoid taking the painkiller Tylenol, the bestselling form of acetaminophen. Speaking alongside Health and Human Services Secretary Robert F. Kennedy Jr., himself a vaccine skeptic, Trump stopped short of opposing all vaccines. “Don’t let them pump your baby up with the largest pile of stuff you’ve ever seen in your life,” he said.