If his weight at two and half years is 10 kg and height 94cm then he is thin but long. But only on milk now is not good. Stop bottle and milk all together. Give him soft food to eat or else let him be hungry and nothing in between. You may give him milk based food example kheer,curd,burfi. Basic principal has already been elaboratated earlier. He must be iron deficient, please him some iron supplement example sup hemsi 5ml once a day for hundred days.

There is slight reduction in hemoglobin and the rest is within normal limits and take iron capsule like Hemsi capsule

Common cause is anaemia//lack of blood. You can stgart cap hemsi 1 before dinner.
Get your hb//haemoglobin level tested.
are you having any abnormal monthly periods.
Feel free to ask after details.