The eligibility criteria for NATA says that the candidate should have secured at least 50% aggregate marks in Physics, Chemistry & Mathematics. But you have 45% marks in PCM, thus makes you ineligible for the examination. For admission to B.Arch, you have to pass either in JEE Main paper 2 or NATA to get into B.Arch. Or you may appear for state level entrance exams like UPSEE etc. Some colleges which don't take admission on the basis of Jee Main paper 2 and Nata score-

• Bundelkhand University, Jhansi
• G.L. Bajaj Group of Institutions, Mathura
• Forth Dimention College of Architecture, Saharanpur
• Axis Institute of Architecture, Kanpur
• ITM School of Architecture and Town Planning, Lucknow
• Sunder Deep College of Architecture, Ghaziabad
• Apeejay Institute of Technology School of Architecture and Planning, Gautam Buddh Nagar
• R.R. Institute of Modern Technology, Lucknow etc

But for admission to this colleges you need to write entrance exam.