Oh No! Did Jessica Simpson's Baby Daddy Cheat On Her? (DETAILS)

Jessica Simpson and her fiance/baby's father Eric Johnson may be diving head first into a really bad situation!

PHOTOS: Jessica Simpson Shows Off Baby Maxwell During A Birthday Party!

Eric, who met Jessica while he was still with his ex-wife Keri Johnson, was supposedly still intimate with his ex after moving onto Jess, Star magazine is reporting.

Keri's friends are extremely upset about how the ex-NFL player handled leaving his wife for Jess. 

DETAILS: Jessica Simpson Says She Didn't Think About Her Weight During Pregnancy!

One of her friends allegedly said:

"He’s a two-timing cheat! He was still having sex with Keri after he started seeing Jessica. She needs to think twice before marrying him. He’s already cheated on her once — he’ll most likely do it again.”

That's really messy... Is there a proper way to leave your wife for a new woman anyway? 

These two, who are engaged but not yet married, have a healthy happy baby named Maxwell who was born just a few weeks ago; we hope their little girl has solidified Jess and Eric's relationship!

SOURCE: Radar Online || Photo Credit: WENN