Listen bro!. Im taking time to write this because I know how you feel. I had exactly the same kind of problem 4 years ago.
Used to get these crazy attacts at least once in a month. With heartbeats, numbness in hands and sometimes under my feet, chest pain, problems with breathing. I thought I was gonna pass out or die everytime.
Got rushed to the hospitale with an ambulanse twice! I was there for 4 days the first time, and overnight the secound.
The doctors did all kind of tests, kind of ultra sound thing on my chest, cardio, monitoring, hormone check etc.. Gave me a device that i wore for a whole week to automaticley check my BP every 20 mins.
In the first couple of days the BP was little bit high sometimes because of the nervousness, and then it came back to normal.
After months of hospital vistiations and research THEY DIDN`T FIND ANYTHING.. I was so frustrated, because I ment that it had to be something wrong with my heart, why else I keep getting these nasty attacks.
After almost a year they came to the conclusion that these attacks are anxiety attacks, and put me on SSRI. That shit made me a zombie, so I stop using it.
Now 3 years and many attacks later, I`ve learned to control them.
Anxiety attacks is not easy to get completley rid off. You have to train your self, dont be scared, ( even though its easier said then done ), STOP STRESSING, stress is factor nr 1 for anxiety no doubt.
Then we have steroids. Steroids can cause anxiety attacks for those who is prone to it.
You said that you had this since you were 14, that means you are prone to have anxiety attacks. Steroids is not the main reason why ppl have these attacks, but they sure make these attacks to come more often and maybe even feels stronger.
I`ve had these attacks before and after I started using steroids, and I can say with certainty that I know what I'm talking about when it comes to steroids and anxiety.
NOW I`m not your doctor, and are only explaining my former situation to you. But, based on what I read, you are in the same palce I were 4 years ago, desperately looking for answers and hoping that weight lifing and steroids dont have anything to do with you condition.
Steroids rearly create the anxiety attack condition by its own, but if you already have anxiety problems, it will make it worse.
Keep going to your doctor, follow thier advice, stop stressing and think wisley.. Im sure its gonna be alright bro