Aw mama, that heaviness you're feeling after vitamins could be the iron content, kaya ang dami ng preggy friends ko na nakakaramdam ganyan, lalo na sa first trimester! Try taking your vitamins with food or right after eating, and if the sipon won't go away, please check with your OB na because that's something they should know about, especially this early sa pregnancy. Rooting for you mama, first time is really overwhelming pero you're doing great!