“I get insanely jealous in relationships”

What could be going on

Jealousy: Fear of losing a partner to a rival fits; check whether there's evidence.

Anxious-preoccupied attachment: Doubt that partners will stay fits; check how you feel when apart.

Abandonment/instability schema: Expecting to be left fits; check whether past partners actually left.

Mistrust/abuse schema: Expecting betrayal fits; check whether you were betrayed before.

Protest behaviour: Checking and accusing can be protest; check what you do when anxious.

Controls a partner's money, friends or movements: Check whether jealousy turns into controlling their friends or movements.

Also said as

• I check my boyfriend's phone
• I get jealous of my partner's friends
• my husband is jealous of everyone I talk to
• I can't trust my girlfriend even though she's done nothing
• I'm extremely jealous of my partner
• why am I so jealous in relationships