heartbeat awarness

hi, i'm new to this and hope someone can offer me some advice :)

i've been feeling so sick mentally and phisically for the past 6 months! so in july '09, i was feeling so fatigued and my heart was beating so fast and irregular, i just fell asleep as soon as i lay in bed, it was so bad! so after 1 month went to doc and tested my blood. i only had low iron so was told to take supplements.
so for few months i was taking those, eventually made me feel better, although i had heavy head feeling and my heart beat was just weird still, so i somehow became aware of it. i kept having paltipations. so i had ecg then too, and was told i had right bundle branch block, however my doc said that was normal for some ppl?! but i tried to calm myself, however i developed acid reflux from all iron tablets then stopped taking them. i had blood test after and all normal. but then my stomach was hurting.
but now in jan, i've been stressed out for few weeks, coz of all tht pain and some fam issues. so my question is that now in past week, i've all of a sudden stopped having paltipations, and when i exercise i get so tired, i feel dizzy, feel like my heart is just weak, and my beats are just hard to feel and irregular again. but my iron is ok. i jst feel like my heart got weakend due to my low iron and jst cant take it anymore, i've been to doc but he jst listened to my heart and said tht i hav a good heart?! he always says tht. but its jst like one day i had fast paltipations and day afta i can barely feel it... please comment if anyone knows wat this could be or if anyone has had similar symptoms. thanks!

[mammo]

Stress can make your heart rate rise,  which means it will beat faster and harder.  Getting your stress under control will help with this.  Because of your age I seriously doubt it's your heart, but constantly worrying over what may be wrong, can increase your stress.  Which in turn causes the heart to speed up etc, it's a viscious cycle.You also may want to see a psychiatrist to get a proper diagnosis as you also have symptoms of depression, but only a professional can diagnose this. Your doctor doesn't appear to be addressing these problems and you need to get help with them.
Take care...