don't know about the 'heart-shaped' leaves ... although we all have
different ways of describing things ... here's a picture of a buddleia
flower and some of the leaves, together with the butterflies that are very
attracted to the plant

http://www.butterflygarden.co.uk/pla...66_p_ra_st.htm

.... if yours is like this, then you probably have a buddleia. if not, i
have the feeling it might be a lilac. do you have any pictures of your
plant that you could post up to your webspace?