How can you naturally boost your serotonin levels?

Cause I have veryyy bad anxiety where I get panic attacks all day everyday and i'm becoming super depressed cause of it and dont want to leave the house to do anything. I dont want to take meds, and I am seeing a therapist but she's not helping very much. I mean she gives good advice, but I feel like crap a day later. So what are some natural things to eat or do to boost serotonin? and i would work out but when my heart rate goes up it brings on a panic attack cause it feels like one. I feel like I'm going crazy.