hi i woundered if any one can help me?

i have a five year old turkish van, FELIX (or turkish water cat as commonly known) black and white long hair and yes he loves a bath usually when i'm in it, we've had him since he was six months old, i have trained him to come to my whislte and if he runs from me i trained him to stop lie down at my click the finger and point at the floor and he waits to be picked up and he is an outdoor sort of cat. any way back on topic he has never been affectionate or loveing absolutely refuses to be picked up for a cuddle and never been vocal, thas untill september this year when he changed over night quite literally, he came in through kitchen window as usual and started meowing i thought he was hurt as he only spoke when he's hurt so i rushed to him to check as i was checking him he rubbed my face with his giving me a kiss and started purring like mad (wich ive nevered heared him do in five years i had him even when he has a bath he is usually silent and its on his terms too weather he gets in or not), so savouring the moment i fussed him a for a while not like him to stay either for a fuss he usually dashes back out, but anyway while fussing him i must of had about 40 kisses off him and constant purring, not to detur him i left it at that went in room for a game on pc he came in behind me wanting more jumping on comp desk purring and rubbing my hand till i fused him more so i fussed him a boit more only for him to jump on my lap and curl up to sleep he's never done this!! i woundered if it was my cat for a second but it was he's noticably larger than the normal moggy. since then e's jumped on my lap everytime i sit down he comes up to bed when i go have a liedown he's allways purring now he kisses me whenever my face is near his and he also loves my kids and allows them to stroke him (i have twin girls also five and 22 month old) today was a real shocker as he jumped up into my wifes arms for a cuddle and wouldnt get down and stay down untill she made a complete fuss of him wich lasted a good 30 mins. he's never allowed us to pick him up if he sensed you were going to he would hop skip and jump out the window. he's also taken to being indoors so we got a litter tray wich he refuses to use and uses the downstairs toilet to releive himself yes the toilet he cant flush so meows by the door till you do it for him. he's taken to sleeping at the bottom of my twins bed during the night (before this he refused to stay in over night) or shares the bed with wife and i usually cuddled up to me with his head on my arm. he's continued to shock us everyday with his affection and behaviour i was woundering if something was wrong with him and considdering taking him to the vet, as lately hes been eating a tin of cat food and minate later asking for more going outside and woundering retraceing his steps and when we go out for some hours coming back in he looks at me or wife cowers down as if he doesnt recognise us and darts out the door only to stop turn around and comeback in as if he suddenly remembers its me and wife and he is vocal almost everytime he is awake he's also been eating loads and loads and drinking well but loseing a bit of weight i have de-flea'd and de-wormed useing same product since weve had him regularly and upto date with all jabs includeing felv wich he has every year he will only eat felix cat food and drink only semi skimmed milk have tried others but wont drink them. can anyone shed some light on to what maybe wrong with him if anything and explain the not so normal behaviour for him. im worried yet delighted he's found his affectionate side. sorry this is so long winded but tried to give a detailed amount of info. (yes i am a male who is a majour cat lover)