when he texted me i felt that he want me and missing me .but when he saw me outside he showed himself that he doesnt even know me….i dont know why i feel so much love for him….i dont want to love himmm 🙁

hallo everyone .
i am writing here again. me and my ex lives in same building now and two times he saw me with another outside of building .my ex texted me 5 days before to invite me for a cup of tea or coffee with my one more friend .i told him that i dont drink tea or coffee at night because i wont be able to sleep .he added that its up to u .u can for for company..bcz he called my one of best friend and i had to go .but dint drink coffee or tea as i told them my reason .
we were his room and i dint talk to him i was just talking little bit with my friend..
i couldnt understand why he called us ?or even me ?was that to contact with me ..
because after my breakup i dint talk to him ..no call no text nothing….
2 days passed he texted me again saying HI after 20 mint i replied HI (it was seen in whatsapp)
thn after 9 to 10 hours at night 3am he texted me “i know it is awkward to ask but i want to know in straight words and honestly “how you found me as a person”? as we had been togather “……. after reading his text i was confused to think what he actually want to know and why does he need to know my answer .and why ?
and finally yesterday( after 8 hours) i replied, “you were a nice person ” after that he dint replied any thing and this text was seen by him .

i just want to know what is the reason why is he doing like this ? he is already in relationship he told me before 21 days and left me ..(described in my earlier post ).and now how should i responce ?…