Do I need root canal in these filled tooth? Will my cavity get severe? (Photos)

i got my molars filled with these dark coloured filling about an year ago. there was pain when i applied pressure with my finger on them at hat time. but now after filling no problems faced except a little senstivity on them for about 2 seconds from very chilled or hot water that too not always. do i need a root canal? is x ray be important to identify any problems? will my cavity get severe and will form an abscess? what are the signs that i should not ignore and seek dentist. iamveryanxious!