20 y/o few symtoms. Talked to the doctor already

[fctte]

Hi, I am a 20 y/o male. I so have health anixiety and sometimes I am not sure when or when not to be worried.
Here's a bit of a background. I've had no diagnosed heart issues ever in my lifetime. Indo though have scoliosis with a chest curve on the heart side. And doe years now I've had troubles running even short distances, I'd get out of breath. Had no trouble walking though. Can walk for miles non-stop
Not overweight, very skinny. No issues really before like 3 weeks ago.

I've been recently experiencing few symtoms that resemble heart failure. I talked to doctor over the phone and been brushed me off as "you're too young, it's fine", she said that since my legs aren't swollen and I don't have breathing issues (which I do a bit and I told her) she told that it's probably anixiety and whatever... and I know that's how it usually goes with young people and HF, you just get dismissed till it's too late

So for a while now I've had an irregular heartbeat. When I lay down it's about normal but when I stand up it's close to a 100 beats per minute. I didn't measure my heartbeat this morning but yesterday it was 59/m when I just woke up and today it was in the 80s-90s in the evening even when I was laying down. Tomorrow morning I'll measure my hb and elaborate more on that

I've been starting get those infrequent pokes in my heart and rare squeezes. I only get them few times a day and they used to be non constant. But now the frequency hasn't changed by they seem to last longer. Still not long, few minutes max I think. They are about 4/10 on he pain scale

On breathing. I have been breathing a bit more heavily, like I have to take deeper ans like louder inhales for a bit at certain times. It seems to be getting more frequent, but I am not sure if this is the breathing symptom or I am just noticing it more now that I am thinking about it more

And the last one. Coughing. I haven't coughed much until this evening.when I coughed a bit and now I just continuosly feel hoarse in my throat.

As I said I did talk to the doctor and she brushed me off as "it is not a stroke or a heart attack, so you're good and you are way too young"
Considering that I just wanted to ask, does that sound like a heart failure to you? I mean I don't want to outsmart the doctor. I want to outsmart the disease.

From what I understood: Heart failure doesn't come from nowhere it is a follow up disease of something else. I can't really afford doing major scans, not financially not morally unless there are serious suspicions. So what I thought of doing is that probably the only cause of heart failure I could have is coronary artery disease and the way to find it is to measure my cholesterol. I did do a blood test for that and now I'm waiting for the result and I thought of acting on whatever the result shows. If it does find the CAD then I gotta go deeper. If not.. oh well then..

What is your opinion on what should I do and what do I have?