For the last several months this year, my dad was diagnosed with gastric lymphoma but looks like hes going to survive but then a few days ago . Ky grandma recently died of lung cancer.

Lately I cant stop thinking about having about having various illnesses and cancers all the time and constantly look if I have any of the symptoms of the various diseases .

I went to the doctors a few months ago because I thought I was having a heart attack, but he took a sample of my blood and did an xray on chest and said they found nothing.
They said in was fine but I was very stressed. I dont know . I feel pain all the time , and have aches all around my body usually , stomach l, chest, and back that's the most concerning.

Please anyone with any training in medicine, please give me some advice.