Lindsay Lohan and her new love Riley Giles recently planned to become engaged after fears of facing an unplanned pregnancy.

“Lindsay was terrified,” says a Star Magazine source. “She’s also gained a lot of weight, and she started worrying that it was from being pregnant.”

“She just figured out how to get sober-she’s certainly not ready to be responsible for a child now.”

When LiLo told Riley that she may be pregnant, he got right down on one knee and proposed:

“He was actually pretty excited. And he did what he thought was right and proposed on the spot.”

Lindsay got her cycle a few days later, but the star was touched by her BF’s rush to action:

“It made her want to trust him completely, which is something she hasn’t been able to do with a guy in a long time.”